In this article, we analyse the implementation and change of a specific school reform in Germany using the example of external school evaluation in Lower Saxony: the school inspection. We investigate how and why a newly implemented reform is itself subject to reform shortly afterwards. We begin with a historical background of German school reforms over the last 40 years. Then, we consider school reforms through the lens of organisational theory. Finally, we combine the historical and theoretical perspectives on school reforms placing particular emphasis on more recent developments in external school evaluation. Based on these considerations, we elaborate some theses on reform and routine in schools.