The introduction of the national evaluation system in the Norwegian education system can be described as a shift in the Norwegian educational policy from the use of input oriented policy instruments towards a more output oriented policy. The new tool-kit consists of different evaluation tools, such as standardised tests, diagonistic tests etc. which create new expectations to schools and principals. On the one hand, this article focuses on the policy purposes of the evaluation tools as they are formulated in policy documents. On the other hand, it investigates principals' perceptions of the use of the evaluation tools to improve student achievements. A text analytic approach focusing on language and discourse is used to analyse policy documents. The analysis of the principals' perceptions is based on a quantitative analysis of survey data and Structural Equation Modeling is applied as an analytic technique. Based on the analysis, questions can be raised whether all the policy purposes can be fulfilled or whether the tools might produce other effects than the objectives assigned to them. Problematic aspects related to the tools' modes of regulations and thereby the choice of tools are discussed, as well as inconsistencies between the policy purposes and the use of tools in practice. (Contains 1 table, 9 footnotes and 3 figures.)