In this study the relationships between writing instruction and functional composition performance were analyzed. The data were obtained in a national assessment on the language proficiency of students in the third year of Dutch secondary education (age ±15). Multivariate multilevel analysis showed that 10 out of 36 instructional characteristics were related to functional composition performance. The effective instructional characteristics included: instruction and exercises in writing functional texts, writing for a specific purpose, tailoring to a particular audience, global rating of writing products by the teacher, and frequent evaluation of Dutch language proficiency through teacher-made tests and written assignments. No effects were found for the rather popular subskill exercises on idiom, syntax, spelling and punctuation, and for pre-writing activities, text revisions and peer-review. Furthermore, the effect of instructional characteristics was often different on one task than on another. Finally, there was little differential effectiveness for different groups of students. If one instructional characteristic was more effective than the other, this was generally true, to an equal degree, for boys and girls and for promoted and non-promoted students.