The ideal that has been guiding evaluation systems in Brazil, at the various levels of education, is based on the premise that assessment can improve the quality of education assessment, as a political position, is a by-product of the concern with the efficiency of schools in achieving their learning objectives, and as a way of making teachers responsible for their students’ failure. Some characteristics demonstrated in these processes suggest that competitiveness is a parameter for ensuring better performance of students and schools. The Exame Nacional do Ensino Médio (National Secondary Education Examination ) (ENEM) is seen as an opportunity for self-assessment, by students, as support for future choices in relation to the job market and continuation of higher education. This text is part of a study carried out for the Doctorate Program in Education. It discusses, through the analysis of statements by teachers, how the assessment practice of the ENEN is affecting teaching practices in secondary education.