  Achievement gaps refer to the difference in the performance on examinations
of students belonging to different social groups. Achievement gaps between
ethnic groups have been observed in several countries with heterogeneous
populations. In this paper, we analyze achievement gaps between ethnic
populations in Brazil by studying the performance of a large cohort of senior
high-school students in a standardized national exam. We separate ethnic groups
into the Brazilian states to remove potential biases associated to
infrastructure and financial resources, cultural background and ethnic
clustering. We focus on the disciplines of mathematics and writing that involve
different cognitive functions. We estimate the gaps and their statistical
significance through the Welch's t-test and study key socio-economic variables
that may explain the existence or absence of gaps. We identify that gaps
between ethnic groups are either statistically insignificant (p<.01) or small
(2%-6%) if statistically significant, for students living in households with
low income. Increasing gaps however may be observed for higher income. On the
other hand, while higher parental education is associated to higher
performance, it may either increase, decrease or maintain the gaps between
White and Black, and between White and Pardo students. Our results support that
socio-economic variables have major impact on student's performance in both
mathematics and writing examinations irrespectively of ethnic backgrounds,
giving evidence that genetic factors have little or no effect on ethnic group
performance when students are exposed to similar cultural and financial
contexts.
