This paper presents the first findings from a survey, administered to 421 Italian in-service primary teachers, on their beliefs regarding the knowledge and skills investigated by the national standardized assessment (INVALSI) tests, their proximity to didactic practices in Mathematics and the role they assume within the school context. The case presented in this paper is discussed in order to investigate the way teachers interpret data coming from standardized assessment and if/how they use them in their teaching practice. Findings show an overspread meta-didactic conflict generated by teachers' difficulties in interpreting INVALSI tests and in using them coherently with the framework on which the tests have been designed.