The relationship between intelligence and academic achievement throughout middle school: The role of students' prior academic performance

• Intelligence only indirectly predicts academic achievement.
• Prior academic achievement plays a mediation role.
• An association between Gc and academic achievement is stressed.
• Cattell’s investment theory is applied to the educational field.

The association between intelligence and academic achievement is well established. However, how this relationship changes throughout schooling remains undefined. In this 3-year longitudinal study, 284 Portuguese middle school students completed three reasoning subtests (abstract, numerical, and verbal) by the end of 7th grade (intelligence), and their academic grades were collected at the same time (prior academic achievement, AA7) and by the end of 9th grade (final academic achievement, AA9). The main findings show that i) when intelligence and AA7 are analyzed as two independent predictors of AA9, AA9 is best predicted by intelligence when considering the mediation effect of AA7, and ii) the inclusion of AA7 in the pathway between intelligence and AA9 produces a considerable increase in the predictive validity of intelligence. Implications for cognitive assessment and psychological practice are emphasized based on this Gf–Gc relationship.