Each student has a different amount of time to fully understand information, students with high academic ability (UA) need less time than students with low academic ability (LA). Teachers should apply learning models that can facilitate their study time according to their individual needs. The aim of this research is to assess which learning model is most optimal in reducing the gap in understanding mathematical concepts between UA and LA students. Apart from that, this research also evaluates the effectiveness of implementing the flipped class (FC) model in increasing students' understanding of mathematical concepts, compared to the problem-based learning (PBL) model and conventional learning models. The research method used was the N-Gain Test and ANCOVA. The research results show that the FC model is the most optimal in reducing the gap in understanding mathematical concepts between LA and UA students. In addition, both FC and PBL models have proven effective in increasing students' understanding of mathematical concepts when compared to conventional models. Future research could consider combining the FC model with PBL or other learning models to see whether combining these models can improve students' understanding of mathematical concepts more significantly.