Question: Does instruction in grammar improve writing?
Answer: “Students who were taught systematic grammar scored better on grammar tests but did not score better on essays.” JJ Heiman. 1988. P. 211.
Comment: Teachers can rather easily replicate this research. Maybe they should. RayS.
Title: “Annotated Bibliography of Research in the Teaching of English.” Ed. JD Marshall and RK Durst. Research in the Teaching of English (May 1989), 208-222.