This paper describes the methodology, applicability and utility of the Raven Progressive Matrix (Raven Test) and the Brazilian Intellectual Probe (TSI), comparing them with school achievement in a typical medium-size urban community of Northeastern Brazil. 388 schoolchildren (7-17 years old) were examined, with 371 Raven tests applied. Only 231 TSIs were completed, since 106 students were illiterate. School grades were obtained for all participants. A questionnaire evaluating school resources, and teacher profiles was answered by 200 teachers. Raven and TSI test scores were highly correlated (r = 0.53, p < 0.001), but both correlated weakly with overall school grade (r = 0.22, p < 0.001 and r = 0.12, p < 0.07 respectively). For individual school grades, the Raven scores showed statistically significant correlation with all subjects, while the Brazilian TSI presented statistically significant correlation only with geography, history and sciences. Boys' mean scores were higher than girls' for both the Raven and the TSI Tests, but for the school grades girls performed better. In general, level of cognitive development was below that expected for children in the age-group analyzed.