The impact on student achievement of an assessment for learning teacher professional development program

Assessment for Learning (AfL) can increase student achievement. However, teachers find implementing AfL coherently difficult, as it requires complex professional competence. In this experimental study, we investigated the effect on student achievement of teacher professional development for AfL based on the dynamic approach (n(teachers )= 41, n(students) = 599). The dynamic approach includes four principles: (1) a competence-based approach, (2) adapting to teachers' needs, (3) explaining underlying mechanisms, and (4) supporting teachers in acquiring the competences. We found a positive effect (d = 0.27) on student achievement. Recommendations for teacher professional development and future research are presented.