This file contains a summarized manual and all indicators of the ADAPT instrument. ADAPT stands for Assessing Differentiation in All Phases of Teaching. The ADAPT-instrument was developed based on research on differentiation in primary education (Van Geel et al., 2019). The 23 indicators are scored based on a classroomobservation, combined with an interview with the teacher. The development, psychometric quality and suggestions for use in practice are described in Van Geel et al. (2025). van Geel, M., Keuning, T., Frèrejean, J., Dolmans, D., van Merriënboer, J., & Visscher, A. J. (2019). Capturing the complexity of differentiated instruction. School Effectiveness and School Improvement, 30(1), 51–67. https://doi.org/10.1080/09243453.2018.1539013 van Geel, M., Keuning, T., Dobbelaer, M., & Glas, C. (2025). Assessing Differentiation in All Phases of Teaching (ADAPT): Properties and Quality of the ADAPT Instrument. Education Sciences, 15(11), 1530. https://doi.org/10.3390/educsci15111530