<p>SLAT-Thinking is the only test that evaluates and distinguishes stages of approaches through performance. Although SLAT-Thinking shows evidence of internal validity, its external validity has not yet been examined. In this paper we study the predictive and incremental validities of SLAT-Thinking. Two models were tested. The predictors were inductive reasoning, SLAT-Thinking approaches and Learning Approaches Scale (EABAP) approaches. The outcome was the Brazilian large-scale exam that evaluates the students that finish secondary education. In both models, the superficial approach of SLAT-Thinking was the main predictor, followed by inductive reasoning. The inductive reasoning and both the deep and superficial approaches of SLAT-Thinking were positively associated with academic achievement. while the deep intermediate approach was negatively associated to outcome. Non-linear relationships (positive and negative associations) were found in the two EABAP approaches with the outcome. This study shows evidence of predictive and incremental validity of SLAT-Thinking.</p>