Samenvatting

Meta-analyses on the effectiveness of Montessori education report positive outcomes on both academic and social measures. However, Montessori schools vary considerably, and there is limited empirical literature examining how differences in implementation affect outcomes. To better understand the effectiveness of Montessori education, it is essential to examine the quality of its implementation and the outcomes that follow. Therefore, building upon instruments designed to measure Montessori implementation, this study strengthens the Dutch Teacher Questionnaires for Montessori Practices Revisited (D-TQMP-Rs) and examines validity evidence. In addition, this study explores how Montessori principles are implemented in Dutch Early Childhood and Elementary settings. Results provide initial validity evidence for both the Early Childhood and Elementary versions of the D-TQMP-R, with coherent factor structures and acceptable reliability, though limitations in discriminant and convergent validity remain. Montessori principles appeared to be implemented at a reasonably high level overall. The D-TQMP-Rs offer promising tools for assessing implementation of Montessori education, suitable for research and reflective practice, although still requiring further refinement.