  The Brazilian National Assessment of Secondary Education (ENEM, Exame
Nacional do Ensino M\'edio) has changed in 2009: from a self-assessment of
competences at the end of high school to an assessment that allows access to
college and student financing. From a single general exam, now there are tests
in four areas: Mathematics, Language, Natural Sciences and Social Sciences. A
new Reference Matrix is build with components as cognitive domains,
competencies, skills and knowledge objects; also, the methodological framework
has changed, using now Item Response Theory to provide scores and allowing
longitudinal comparison of results from different years, providing conditions
for monitoring high school quality in Brazil. We present a study on the issues
discussed in Natural Science Test of ENEM over the years 2009, 2010 and 2011.
Qualitative variables are proposed to characterize the items, and data from
students' responses in Physics items were analysed. The qualitative analysis
reveals the characteristics of the exam in these years: long items, only a few
of them demanding more complex reasoning, a characteristic of problem solving
skills. The analysis of student performance also reveals that learning physics
is not attained, with a percentage of correct answers on items that is almost
always small, and that items that require some type of disciplinary knowledge
or require use of mathematical reasoning presents a performance significantly
weaker.
