Evaluation systems of various types are an integral part of a country's education policy space, within which they are supposed to have the basic functions of enhancing accountability and supporting school development. Here we argue that in a crowded policy space evaluation systems may interfere with each other in a way that can have unintended consequences and create new 'policies by the way' that are not the result of intentional policy decisions. To shed light on this argument, we examine five of approximately 30 evaluation systems operating in the Swedish education system. Our analysis examines a situation in which many evaluation systems are doing almost the same thing, i.e. collecting a similar and limited set of quantitative data, and addressing the same local governance actors with the primary goal of supporting school development in the same direction. By doing so, these evaluation systems could thus give rise to several unintended consequences, including a scaling down of the school law and curriculum, multiple accountability problems, increased administration and new intermediary job functions at the level of local education governance.