The role played by measurement in education as well as in the job carried out by an educational psychologist within school is reviewed. Three important measuring devices are examined, so as to show the kind of information that is needed in different areas: the exams teachers give regularly to students in the classroom, the college entrance test, and the tests administered in programs for national or international student assessments. Therewith, a discussion about how to achieve sound educational measures is presented. Finally, some points of interest are highlighted as far as the job of the educational psychologist within school is concerned and also in the more general field of education.