This case study explores the strategies, processes and outcomes of an education reform in Poland which was introduced in 2009 and substantively changed the school inspection system. Its analysis looks in particular at the co-operation between the central and the local level throughout the implementation of the programme. In order to address the shortcomings of the prior inspection system, the reform combined internal and external evaluation in school supervision practice and put greater emphasis on collaboration among stakeholders. The results of the analysis show that the reform has had a great impact on the organisation of inspectorates, introducing modern principles such as teamwork and self-evaluation. Also, it affected the attitudes of important actors in the education system regarding the relevance of data to support internal and external school evaluation. The overall goals and aims of the reform gained the support of the various stakeholders. However, the implementation and communication processes were seen as deficient, especially in terms of a lack of capacity to roll out the reform as well as a lack of trust/disbelief that evaluation can be used for improvement, rather than the expected punitive purposes. Nevertheless, the reform achieved first structural steps towards building a culture of self-evaluation, which had thus far not been part of the Polish education system.