This paper reviews research on outcomes of writing programs for students in grades 2 to 12. Studies had to meet rigorous standards of research including use of randomized or wellmatched control groups, measures independent of the program developers, researchers, and teachers, and adequate sample size and duration. Fourteen studies of 12 programs met the standards. Twelve (86%) were randomized, two matched. Programs were divided into three categories. Student achievement effects on writing were positive on average in all categories (Effect Size=+0.18), with similar outcomes for writing programs focused on the writing process (ES=+0.17), those using cooperative learning (ES=+0.16), and those focusing on interactions between reading and writing (ES=+0.19).
Slavin, R.E., Lake, C., Inns, A., Baye, A., Dachet, D., & Haslam, J. (2019). A quantitative synthesis of research on writing approaches in grades 2 to 12. London: Education Endowment Foundation.