Reading and writing are critical to students' success in and outside of school. Because they draw on common sources of knowledge and cognitive processes, involve meaning making, and can be used conjointly to accomplish important learning goals, it is often recommended that reading and writing should be taught together. This meta-analysis tested this proposition by examining experimental intervention studies with preschool through high school students to determine whether literacy programs balancing reading and writing instruction strengthen students' reading and writing performance. To be included in this review, no more than 60% of instruction could be devoted to either reading or writing. As predicted, these programs improved students' reading, resulting in statistically significant effects when reading measures were averaged in each study (effect size ES = .39) or assessed through measures of reading comprehension (ES = .39), decoding (ES = .53), or reading vocabulary (ES = .35). The programs also statistically enhanced writing when measures were averaged in each study (ES = .37) or assessed via writing quality (ES = .47), writing mechanics (ES = .18), or writing output (ES = .69). These findings demonstrated that literacy programs balancing reading and writing instruction can strengthen reading and writing and that the two skills can be learned together profitably.