Many instruments for school self-evaluation have become available in primary education; however, they vary in focus, quality and type (e.g., questionnaires, tests, observations, classroom consultation, quality maps, quick scans, etc), creating problems for schools in selecting instruments fitting their specific situations. Research has been conducted to design a reliable and valid assessment framework for school self-evaluation instruments. Three research questions will be addressed in this study. First, what contents and criteria should lay the foundation of an assessment framework for school self-evaluation instruments? Second, what scientific criteria should be taken into account to construct a reliable and valid framework that produces consistent assessments? Third, how can such a framework be most useful for schools? Several research methods were employed; including a literature scan approach, including theoretical perspectives of accountability and school improvement, a focus-group approach, and a try-out to test the first draft framework. The try-out shows a fairly high inter-rater reliability. However, it is concluded that a fair within-group comparison of the instruments on the Internet should include subgroup-specific overviews dependent on the focus of the school self-evaluation instrument (accountability, school improvement, or both focuses). (Contains 2 notes, 3 tables, and 1 figure.)