Introduction
Although educators often disagree about many other aspects of literacy, there appears to be universal agreement that the primary goal and purpose of reading is to comprehend text—to understand what we read. Even more impressively, there is a consensus about the nature of comprehension. Comprehension is not just the by-product of accurate word recognition. Instead, we know that comprehension is a complex process that requires active and intentional cognitive effort on the part of the reader.

Development: Prior Knowledge, Background Experience, and Vocabulary
It is difficult to over-estimate the influence of children's prior knowledge and their experience. In their review of children's learning from text, Alexander and Jetton (2000) conclude, "Of all the factors (involved in learning from text), none exerts more influence on what students understand and remember than the knowledge they possess."

Over the past three decades, research findings have consistently demonstrated how prior knowledge and experience influence reading comprehension (Lipson 1982). Simply put, the more accurate and elaborated knowledge readers have about the ideas, concepts, or events described in the text, the better they will understand it. On the other hand, limited information and/or misconceptions create obstacles to comprehension. When people (not just children or poor readers) read unfamiliar text, they read more slowly, they remember less, they construct meanings that are inconsistent with the author's, and they sometimes reject the text information outright.

In their important book, Preventing Reading Difficulties in Young Children (Snow, Burns, and Griffin 1998), a panel of nationally renowned experts concluded that

The breadth and depth of a child's literacy experiences determine not only how many and what kinds of words she or he will encounter but also the background knowledge with which a child can conceptualize the meaning of any new word and the orthographic knowledge that frees that meaning from the printed page. Every opportunity should be taken to extend and enrich children's background knowledge and understanding in every way possible, for the ultimate significance and memorability of any word or text depends on whether children possess the background knowledge and conceptual sophistication to understand its meaning.

This conclusion highlights the strong connection between readers' prior knowledge and their vocabulary development.

The importance of vocabulary development as a major contributor to reading comprehension has long been acknowledged and widely studied (see Beck, McKeown, and Omanson 1999). In Preventing Reading Difficulties in Young Children, the authors describe why vocabulary development might predict reading comprehension:

Written text places high demands on vocabulary knowledge. Even the words used in children's books are more rare than those used in adult conversations and prime time television. Learning new concepts and words that encode them is essential to comprehension development.

There is a reciprocal relationship between readers' prior knowledge/vocabulary development and their ability to read and understand a wide variety of texts. Not surprisingly, the research suggests that English language learners (ELL) " . . . who develop a strong linguistic and cognitive base in their primary language tend to transfer those attitudes and skills to the other language and culture (they are learning)" (Ovando 1993), and are more successful at learning to read and write in English (Hudleson 1987).

Good prior knowledge and appropriate experiences certainly enhance comprehension, but wide and engaging reading also expands vocabulary and promotes conceptual development. The massive amounts of vocabulary that children need to learn, and that most do learn, has led many researchers to the conclusion that most vocabulary must be acquired incidentally through wide, frequent reading. There is evidence that reading materials are far richer in vocabulary content than oral language. There is also some evidence that students can be taught strategies that increase their ability to derive the meaning of words that they encounter in their reading.

Experience with books helps develop students' vocabulary, but it also helps children to develop a different sort of prior knowledge, equally important for comprehension. Young children often do not fully understand how stories work—especially complex stories with multiple problems. Researchers have found that young children often understand and remember only some parts of stories (Lipson, Mosenthal, and Mekkelsen 1999).

As children grow, they read and hear increasingly complex texts, and they become more able to grasp the subtler aspects of them. Not surprisingly, children not only understand them better while reading, but they are also more likely to include these components in their own writing. By sixth grade, young readers and writers should be able to use a wide range of knowledge, extensive vocabulary, and broad experience to understand and write texts.

The Influence of Text: Understanding Different Types of Texts
Even when readers have much experience and good prior knowledge, their comprehension varies depending on the type of text they are reading. Certainly it is no surprise that "harder" material is more difficult to understand than "easier" material. But what makes a text harder or easier to read and understand?

Some of the factors are important for all readers, and others are more important for beginning readers than for more mature and highly skilled readers. For example, the relationship between the pictures and text can make a big difference in how well very young children understand a story. Indeed, research suggests that pictured events and concepts are significantly more likely to be recalled than non-pictured events (Lipson et al. 1999). If the pictures are central to and support the main themes and ideas of the story, this is good. If, however, the pictures are not supportive, or draw children's attention to unimportant side events (called "seductive details") this can pose problems (Alexander and Jetton 2000). Older, more mature readers do not rely so heavily on pictures to comprehend the stories or texts they read.

Some features of text influence comprehension for all readers. Aspects of text such as its structure, complexity, and genre affect understanding even when readers are very accurate decoders (Goldman and Rakestraw 2000; Lipson et al. 1999).

Text Structures: Narrative
Generally speaking, we organize texts in two large categories: narrative (stories) and exposition (explanation of facts and concepts). These two types of text are different in both purpose and organization. For example, people generally read stories for entertainment, although we may learn from them as well. We read expository text to learn new or clarify old information, although these texts can be extremely interesting and entertaining.

Narratives typically share a common set of features and structures called a "story grammar" (Stein and Glenn 1979). Readers who understand how stories are organized can use this information to help them understand better. When the features of narrative texts are "mapped," children often read and comprehend the stories better and more easily. All narrative texts have

• a setting, either physical or psychological (time/place/mental state)
• characters, the major players in the story
• a problem, or initiating event, something that gets the story started
• important events, related to the problem
• an outcome or resolution, events or consequences that resolve the problem

In addition, most narratives have a theme, a major idea or important concept that the author is trying to convey. There may be more than one theme in a complex narrative, and these ideas are generally more universal than concrete (e.g., "friends stand by each other and help out when needed").

Although children often find narratives easier to read, they may not always understand the more subtle aspects of stories such as the motives or goals of characters or the theme of the story. In addition, there are different genres of narrative texts, and children do not usually have extensive experience with all these different types of stories. For example, they may be quite comfortable reading and understanding simple realistic fiction, but they may not have encountered historical fiction or more sophisticated fantasies. Both exposure and good instruction are usually needed to help children read and understand a broad range of different genres.

Text Structures: Exposition
Expository texts are organized differently than narratives because they are written for a different purpose. We read exposition to learn new information, about a different point of view, or to clarify confusions.

The ideas within a text can be organized in a number of different ways. Teachers and children often focus on the sequence of events and, indeed, these are important in many narrative stories. In exposition, however, the major ideas and events in the text are often not organized according to sequence, but rather by some other text structure.

Not all text structures are equally easy to understand. Stories tend to be easier to understand than exposition for many young readers and, within expository texts, certain organizational patterns are easier than others (Armbruster 1984). For example, cause-effect is more challenging for children than sequence (see graphic organizers in the discussion of instruction).

How Do Children Comprehend?
Not too long ago, both reading experts and teachers assumed that reading comprehension occurred as a natural by-product of accurate word recognition. However, over the past three decades researchers have pointed to a more complicated explanation. There is strong agreement that comprehension is a complex cognitive activity that relies on excellent fluency, vocabulary, and prior knowledge. In addition, "active interactive strategic processes are critically necessary to the development of reading comprehension," (National Reading Panel 2000). Good readers intend to understand—it is not a passive activity that occurs without effort. Teachers and students alike must understand the active, purposeful nature of comprehension.

The Role of Strategies
Reading ability—both comprehension and word recognition—is facilitated when readers use strategies. Even very young children can and do employ strategies during reading, so a solid reading program should introduce and sustain a strategic approach to reading throughout grades K–6. For children in grades 4–8, strategic reading is absolutely essential. The texts and tasks that readers regularly encounter in those grades are more conceptually demanding, are more complex in both form and function, and often address topics or domain knowledge that is unfamiliar. Importantly, even able readers can benefit from explicit instruction and effective instructional support (National Reading Panel 2000).

The obvious next question is, "Are there some strategies that really help readers and writers to be more competent—to read and write better?" The answer is clearly "Yes," although the particular list of essential strategies might vary slightly from one educator or researcher to another. There are two things that most experts agree are essential to understand. First, the number of these strategies is small—it isn't a long list of discrete abilities. Second, these strategies, individually, are not as important as a "strategic approach." As Dole and others have argued, "The goal of instruction would be to develop (in students) a sense of conscious control, or metacognitive awareness, over a set of strategies that they can adapt to any text they read" (emphasis added Dole et al. 1991).

Becoming strategic is a developmental process; it occurs over time as students encounter increasingly difficult texts and new situations. The same relatively small set of strategies emerges quite early in children's development. Among the most highly useful strategies are making predictions and drawing inferences; self-questioning; monitoring comprehension; summarizing; and evaluating. These strategies, individually, are not as important as a "strategic approach" which allows readers to respond differently to different topics, text, genres, and tasks.

Effective comprehenders often use several strategies at one time. In addition, good readers use strategies in a flexible manner. Reading requires the orchestration of a number of skills and strategies.

The Skill and Strategy Connection
According to Pearson, Dole, and their colleagues (1991), strategies are "conscious and flexible plans that readers apply and adapt to a variety of texts and tasks. . . . Skills, by contrast, are viewed as highly routinized, almost automatic behaviors." Skills are generally thought to be less complex than strategies, which, in fact, generally require the orchestration of several skills.

For example, while summarizing is an effective comprehension strategy, readers cannot summarize texts well without an array of skills. Summarization is likely to help young readers understand and appreciate Mark Teague's lovely fantasy, Lost and Found. However, in order to do this successfully, children would need to pay careful attention to the sequence of events and they need to note surprising details.

Strategies require using several skills or abilities in concert. Individual skills can be very important under some circumstances, but they are generally not, by themselves, sufficient to accomplish the complex jobs required of mature readers and writers. No one set of skills is always linked to a particular strategy. Instead, strategies comprise skill combinations that involve a degree of critical thinking, thoughtful selection, and self-control, which is not true for skills. Thus, they are cognitively more complex, but also more versatile.

As important as strategies are, they generally are not acquired without at least some explicit instruction and attention from the teacher. Effective and mature readers can recruit a variety of skills under any number of circumstances to respond to the varying demands of different texts and different tasks. Even highly skilled readers may not have a flexible and strategic approach to reading. Unlike other aspects of reading, exposure and experience alone do not appear to ensure controlled knowledge and use of strategies.

What Should Comprehension Instruction Look Like?
Fortunately, students can acquire fluency, learn to be strategic, and learn to comprehend more deeply. Even better, we have fairly good information about the type of instruction that promotes good comprehension in students. It is very clear that extensive reading practice is essential in building both fluency and knowledge. It is equally clear that good, explicit instruction in some areas provides additional benefit to students. The National Reading Panel (2000) concluded that there are eight types of instruction that are especially effective in teaching students to comprehend. We will discuss each of these types of instruction (highlighted below) within this somewhat broader framework of instruction:

• Reading Opportunity
• Instructional Support for Comprehension in which we discuss graphic organizers, story structure, pre-reading activities, guided reading, questioning strategies, and fluency
• Explicit Instruction in which we discuss comprehension monitoring, summarizing, and multiple-strategy teaching
• The Added Value of Discussion, in which we describe appropriate cooperative learning opportunities for reading instruction, question answering, and question generation approaches

Provide Extensive Opportunities for Exposure and Practice
Both our own common sense and decades of research highlight the importance of practice in learning to read. There is a strong association between voluntary reading and writing and general reading and writing achievement (Greaney 1980; Morrow 1983). The amount of time children spend reading books is strongly linked to reading comprehension and reading achievement gains (Anderson, Wilson, and Fielding 1988; Taylor, Frye, and Maruyama 1990).

What may not be quite so evident is how important reading practice is to developing both the ability to comprehend and general cognitive competence. As Stanovich (1992) has argued, ". . .reading does make people smarter." In part, this conclusion comes from the fact that wide reading promotes vocabulary development. Research summaries by two recent commissions concluded that both overall exposure to print and independent reading promote and develop vocabulary, reading fluency, and comprehension (National Reading Panel 2000; Snow, Burns, and Griffin 1998). Importantly, ". . .exposure to print is efficacious regardless of the level of the child's cognitive and reading abilities. We do not have to wait for 'prerequisite' abilities to be in place before encouraging free reading" (Stanovich 1992).

Recent research also suggests that extensive reading practice as part of a planned instructional program is a distinguished characteristic of successful schools in all demographic regions. In successful schools, primary grade children engaged in continuous text reading between twenty and thirty minutes each day, while intermediate grade children read as much as an hour a day (see Lipson et al. 2000; Taylor and Pearson, in press). In less successful schools, the amount of text reading time was significantly less. Therefore, effective reading programs must include ample opportunity for students to read appropriately leveled texts. To accomplish this, classrooms must include a large and accessible collection of books (Morrow et. al. 1999; Mosenthal et al. in press; Neuman 1999).

Students must read and create authentic materials if they are going to become genuinely strategic (Brown, Collins, and Deguid 1989; Duffy 1993; Resnick 1987). Although short, contrived texts can be helpful in introducing a skill or strategy to students, students will not be able to develop effective comprehension strategies like monitoring, summarizing, and self-questioning unless they are reading increasingly complex material of appropriately substantial length. Nor will they develop and acquire the rich vocabulary and broad understanding of text structure required to become a reader with excellent comprehension.

This balance is especially delicate in the early grades and for students acquiring English as a second language (ESL), when they may not be able to read materials that will challenge and develop their comprehension abilities and background knowledge. Consequently, many authors recommend using teacher read alouds for comprehension instruction while at the same time using more controlled text for beginning readers to practice word-level skills and strategies (Honig, Diamond, and Gutlohn 2000).

Importantly, different materials require different approaches, combinations, and degrees of effort. The flexible and intentional aspects of strategy instruction really only develop when students read (or hear) fine literature, excellent nonfiction, and a wide range of other real-world materials.

Support Comprehension
Because opportunity and experience are so central to the development of vocabulary and comprehension, teachers must find ways to provide access to texts. Independent reading of texts is important, and a regular silent or quiet reading time should be a part of every classroom routine. In addition, however, teachers need to support students so that they can read and comprehend materials that are just out of their independent reach.

Teachers can support students' comprehension by providing support for reading before they begin reading by building background, introducing key vocabulary, and activating existing knowledge. Good instruction should involve solid pre-reading engagement with ideas, words, and organizational schemes so that students' comprehension is improved. According to Anderson et al. (1985), "Using instructional time to build background knowledge pays dividends in comprehension" and "useful approaches to building background knowledge prior to a reading lesson focus on the concepts that will be central to understanding the upcoming story, concepts that children either do not possess or may not think of without prompting." Although none of these instructional activities is new or novel, teachers usually do not spend enough time on these parts of their instructional plan.

In addition, teachers can enhance students' understanding through instructional scaffolding. Scaffolding had been described as any assistance that allows someone to solve a problem, carry out a task, or achieve a goal that he or she could not accomplish without support (Wood, Bruner, and Ross 1976). Graphic organizers and visual maps are among the very best types of scaffolding for literacy (National Reading Panel 2000).

For narrative texts, story maps work very well. At first, children can be taught a generic map that includes the major elements of story grammar (see earlier discussion of stories). Later on, children can be supported in reading more complex stories by providing maps that frame the particular story they are reading. Sometimes stories are best understood by attending to relationships among the events and not in terms of classic story grammar.

Expository texts are often more complex and variable, so graphic organizers can be especially helpful to young or less-skilled readers. Again, it is important to make sure that the graphic organizer highlights the major organizational pattern of the specific text being read so that the children's comprehension is supported as they "fill in" the parts that will guide them through the selection. As children gain expertise, they should be encouraged to create their graphic depictions of the material they are reading.

Not all children need extensive support during reading, and the degree of support will likely vary depending on the type of text and the students' familiarity with the content of the piece. Many ELL students can benefit from enhanced support. For students who need it, teachers can help promote comprehension by supplying additional information about vocabulary and key concepts; model appropriate comprehension strategy use or support students' efforts to use strategies themselves; and prompt discussion through skillful use of questioning (see discussion below).

A comprehensive reading program should include provisions for flexible and varied supported guided reading of text and effective graphic supports. In addition, it should highlight key concepts and build background for students who need it. The program should also make provisions for text rereadings, sing tapes, and/or simplified summaries for additional experience and practice.

Teach Comprehension Explicitly
Although extensive practice and good supportive reading opportunities are necessary and generally effective, they are not sufficient for many children. Many children require explicit instruction in how to comprehend.

Some students do acquire strategies and learn to use them efficiently without explicit instruction. As we noted earlier, however, sophisticated use of strategies and coordinated skills usually require explicit teaching (Paris, Lipson, and Wixson 1983; Paris, Wasik, and Turner 1991). A good reading program must attend to students' strategic reading development throughout the grades. Since it appears that a relatively small set of strategies is used across many ages, grades, and/or tasks, it makes sense to teach these strategies in all grades. The strategies don't change, but students (in kindergarten and first grade) can use a summary strategy, for example, that includes telling the beginning, middle, and end. By sixth grade, student summarizations would attend to character, plot, problem-solutions, and resolutions.

During explicit instruction, teachers employ a variety of techniques: direct explanation, modeling, guided practice, feedback, and application (Dickson, Collins, Simmons, and Kameenui 1998). Direct explanation is important, because researchers have demonstrated that many students do not seem able to extract critical information from their experiences. They need the teacher to explain exactly what (strategy e.g.) they are learning, how to use it, and why it is important. In addition, students benefit from teacher modeling of complex strategies. As teachers "think aloud" about their cognitive actions, students can see how they could replicate these activities. Guided practice is especially important because strategic reading seems to require that students have "conditional" knowledge regarding the strategies they are learning (Paris, Lispson, and Wixson 1983). This explicit instruction should make clear to students the value of using a particular strategy, or strategies, and should model for students appropriate mental processes. Then, during guided practice, teachers should let students know when and why (conditional knowledge) to use these strategies during reading and writing tasks. As children use their newly acquired strategies in supported contexts, teachers can provide feedback. Finally, children must have ample opportunities to apply the strategies to new texts so that they can acquire independence and self-control.

Discussion Provides Added Value
Researchers have recently found that literature discussion promotes motivation for reading and can also improve students' comprehension. There are any number of possible ways to promote literature discussion, and different approaches appear to benefit children in slightly different ways. As the National Reading Panel (2000) has noted, research supports the effectiveness of cooperative grouping and also any approaches that improve students' question-answering and question-generating abilities. Two approaches to literature discussion that have strong research foundations are "Book Club", developed by Raphael and her colleagues (see McMahon, Raphael, Goatley, and Pardo 1997) and "Question the Author" (QtA) developed by Isabel Back and her colleagues (Beck et al. 1996; Beck, McKeown, Hamiliton, and Kucan 1997).

Whereas discussion is just one component of Book Club, it is the major feature of QtA. Since the primary purpose for QtA is to help students build understanding from text to increase and improve comprehension, we will describe this approach in some detail. The research base for QtA is impressive. Beck et al. (1996) report that, in QtA classrooms, teacher questions and student responses become more meaning-oriented and that students become more active participants in discussion. In addition, when students responded to teacher queries, they were more likely than other readers to go beyond verbatim responses, integrating their own prior knowledge, inferences, or hypotheses in their answers. Importantly, during discussions, students were also much more likely to initiate their own questions and comments.

Conclusion
Successful comprehension instruction requires a sophisticated literacy program, one that includes: diverse literature, both fiction and nonfiction; many opportunities for independent and supported practice; thoughtful instruction before, during, and after reading; explicit teaching of comprehension skills and strategies; and cooperative, collaborative discussion of texts. Because there is such overwhelming consensus about good, research-based instruction in the area of comprehension, educators should expect their commercial programs to support effective practice in each of these areas.

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