This chapter originates from an interdisciplinary research project involving experts in the didactics of mathematics, general didactics and assessment, with the aim of investigating the beliefs and attitudes of primary school teachers on the connection between the INVALSI mathematics tests and teaching-learning processes. The survey was administered in the 2019/2020 school year in the form of a semi-structured questionnaire aimed at investigating: teachers’ awareness of the learning objectives detected by the INVALSI tests, their conceptions of errors in mathematics, the use of the tests in daily didactics, misconceptions about standardised tests and the concept of assessment. The tool was administered to a non-representative national sample consisting of 526 fifthgrade mathematics teachers at primary schools. The analyses presented focused on the one hand on the link between teachers’ beliefs on the type of knowledge and skills detected by the INVALSI tests and on the validity of the tests themselves, and on the other hand on the convictions and statements regarding the teaching practices usually implemented by the teachers. The interpretation of the links that emerged on a correlational basis, between the two blocks of variables, showed how teachers’ beliefs influenced the direction of their didactic choices. Teachers who score high on the considered indices and factors perceive themselves as professionals and believe that learning can and should be constructed. Recognising the validity of the INVALSI tests in relation to the skills they demand of students on the one hand, and their usefulness for analysing, reflecting and planning didactics on the other, affect the type of prevalent use they make of the test in the classroom context: a use aimed mainly at developing skills rather than at teaching-to-test and aimed at improving the didactic proposal to students to help them strengthen their skills.