Writing is a very demanding task, requiring the orchestration of a variety of cognitive resources. For developing writers, it can be especially demanding, as they have not yet mastered important writing processes, skills, and knowledge involved in planning, drafting, and revising text. In the present study, middle school students were directly taught strategies that facilitated the execution of each of these processes. They were also taught the knowledge and skills needed to carry out these strategies. In comparison to peers in the control condition, students in the experimental treatment condition produced essays that were longer, contained more mature vocabulary, and were qualitatively better. These gains were evident immediately following instruction and on a short-term maintenance probe administered 1 month later.Writing is one of the most difficult skills that children are expected to master in school (Graham & Harris, in press). The difficulty of learning how to write competently is reflected in data collected as part of the National Assessment of Educational Progress (Greenwald, Persky, Campbell, & Mazzeo, 1999). At the 4th-grade level, for example, slightly more than 60% of the students tested were classified as "basic" writers, demonstrating only partial mastery of the skills and knowledge needed at that grade level. Another 16% of 4th-grade students scored below this basic achievement level. Similar results were obtained at the 8th-and 12th-grade levels. These findings indicated that the average American student is not a proficient writer, as the percentages of students who performed at or above the proficient level remained approximately 25% at each grade level.Concerns about children's writing have led to calls for improvements in the teaching of writing (e.g., Riley, 1996), with many states and school districts designing and implementing procedures to boost students' writing performance (e.g., Bridge, ComptonHall, & Cantrell, 1997). This is a particularly challenging task, however, as skilled writing requires the acquisition and coordination of strategies for regulating the writing process (e.aimed at improving writing instruction need to help students develop the strategies, skills, and knowledge needed to write effectively.The present study examined the effectiveness of an instructional program designed to improve the writing performance of middle school students. Although the program primarily focused on teaching students strategies for planning, drafting, and revising text, the knowledge and skills needed to support these processes were also emphasized. This emphasis included knowledge about the characteristics of good writing, criteria for evaluating writing, and the structure of expository essays that involved explanation and persuasion (the writing task emphasized in this study). Writing skills that were addressed included constructing a thesis statement and using mature vocabulary, transition words, and different types of sentences. These skills are not only important in constructing a good e...