Mathematical critical thinking skills (MCTS) are essential 21st-century competencies that secondary students must develop. However, prior studies indicate these skills remain underdeveloped due to conventional teaching methods focused on procedural mastery. This systematic review, conducted in accordance with PRISMA 2020, synthesized empirical evidence on instructional strategies for fostering MCTS in secondary education. Searches were performed in Scopus, Web of Science, ERIC, ScienceDirect, and Google Scholar for publications between 2015-2025. From 1,342 records initially retrieved, 28 empirical studies were selected for full analysis. The review identifies five principal strategies: Problem-Based Learning (PBL), Inquiry-Based Learning (IBL), STEM/STEAM, Project-Based Learning (PjBL), and ethnomathematics. Active, student-centered methodologies consistently produced positive effects, with effect sizes ranging from d = 0.40 to d = 1.27. PBL yielded the largest effect (g = 1.03), followed by IBL (g = 0.91-1.27). However, implementation is constrained by barriers including limited teacher training, rigid curricula, insufficient technology infrastructure, and assessment misalignment. Integrative, student-centered approaches enhance higher-order cognitive development and prepare learners for 21st-century demands. Future research should address teacher preparation, methodological standardization, and institutional conditions to ensure sustainable implementation.
Situngkir et al. (Tue,) studied this question.