This research, focused on the study of factors related to academic achievement, was carried out on a sample of 456 elementary school students (8th graders) in the province of Navarre, Spain. The principal aim of the research was to investigate the importance of previous school ranks, inteligence, differential aptitudes, personality and vocational interest as predictors of academic performance. According to the literature reviewed, previous school ranks reveal as the best predictor of performance, while verbal general inteligence (IGV), verbal comprension (CV) and numerical aptitude (AN) contribute significantly to the prediction of criteria. Multiple correlation coefficients reached were: .8406 for Language course, .7727 for Foreing Language, .8308 for Mathematics, .135 for Biology and .8097 for History. Vocational interest and personality revealing a minor contribution to criteria variance explanation.