This study examines whether peer feedback can be a substitute for teacher feedback and which measures can be taken to improve its effectiveness. A pre-test post-test control group design examined the long-term learning effects of individual peer feedback and of collective teacher feedback on writing assignments in secondary education. Moreover, it examined the added value of "a priori" question forms and "a posteriori" reply forms aimed at supporting the assessee's response to peer feedback. The study supports the "non-inferiority" hypothesis of there being no significant difference in students' progress after plain substitutional peer feedback or teacher feedback. Both groups (plain peer feedback "and" teacher feedback), however, improved significantly less than the groups that worked with question or reply forms, confirming the added-value of these forms. Almost half of the students found the received peer feedback helpful, but less than a quarter considered giving feedback an aid in their own learning process. (Contains 2 figures and 6 tables.)