Introduction: Holding a fix or an incremental mindset influence academic performance; we wonder if an intervention would change students' mindsets. The main goal of this study was to design and analyse the effectiveness of an easy to scale intervention to diminish students' belief about intelligence as something innate and fix, and think that we all have an intellectual potential that depends on ourselves to work it and, thus, maximize our performance. Method: The program was designed following the guidelines of brief interventions, because of their numerous benefits, and it was tested with students from first year of Compulsory Secondary Education. To test its efficacy, we ran a study comparing an experimental and control group with one prior and two post-intervention assessments. Results: We observed using a multilevel model that the trajectory of the experimental group was different from the control group, obtaining evidence that students in the experimental group decreased their beliefs about intelligence as something fix. Discussion and Conclusion: This work may serve as a starting point for future work to improve academic performance in a simple, easily replicable and scalable way.