3. Results
3.1. The data
Table 2 lists the number of student for each combination of years, grades, and SEC. “Total” is the total number of students, “Computer”
indicates the number of students that have computer at home, “Internet” indicates the presence of Internet access from home. The table
display some expected phenomena: almost all A1 students have computer and Internet at home; the reverse is true for the SEC E. The table
also shows that the average grade of students in higher SEC is higher than the average grade for lower SEC students. There is an interesting
exception, the A1 students have lower average grades than the A2 students, for all years and grades. Because there are so fewstudents in the
A1 SEC in the sample (since Prova Brasil only measures students from public schools), we will leave them out of the analysis below.
We would like to point out that this research involves the analysis of data records for over 7 million students (the sum of the total entries
in Table 2).