Effectiveness and perceived usefulness of follow-up classroom observations after school inspections in Northern Germany

School inspection is an external evaluation method that aims to promote the improvement of instruction in several European countries. One typical feature of a school inspection is classroom observation. In order to improve the effectiveness of school inspections in enhancing classroom practices in Lower Saxony (a large federal state in Northern Germany), a follow-up classroom observation was implemented at several secondary schools. The aim of the current study was to evaluate the effects of this treatment on lesson development and its perceived usefulness using an online questionnaire. In total, 436 teachers in the treatment group and 161 teachers in the control group participated in the study. The results show a very small effect of follow-up classroom observations on lesson development in schools. Teachers rate the usefulness of this intervention as rather low. However, follow-up classroom observations seem to have a larger impact on lesson development in schools with a lower level of cooperation among teachers.