According to the teachers, every student made progress in selfand peer-assessment in mathematical reasoning with the help of the rubric. The teachers stated that self- and peer-assessment was easier for the students than ameliorating their own work. The project time was too short for some children to learn how to use the rubric for self-regulated working. While adaptations in the dimensions ‘‘correct computations’’ and ‘‘illustrations’’ were easily undertaken, those for the ‘‘procedure’’ and the ‘‘argumentation’’ dimensions caused more problems, especially for children with lower language skills. Both students and teachers stated that the rubric served as a checklist during and after working on a task. The students also viewed the rubric as a time-consuming tool. They realised, however, that this handicap was primarily due to the reasoning tasks and not because of the rubric itself. Further, students understood that rubrics are not needed for every type of task, yet they indicated a desire to use rubrics for appropriate tasks in other subjects as well. Rubrics seem to enhance motivation, according to the children, because they encourage students to aim at reaching a higher level, or even the highest level. Students indicated feeling more secure using the scoring grid because they knew which competence level they achieved and what knowledge and skills they possessed.