Abstract
Introduction Kazakhstan's performance in mathematics in the PISA 2022 assessment remained below the OECD average, highlighting the need for more effective pedagogical approaches to improve students' mathematical literacy. This study examined the effectiveness of a STEM–problem–based learning (STEM–PBL) approach in developing the mathematical literacy of Grade 11 students in geometry. Methods A quasi-experimental pretest–posttest design was implemented during the 2025–2026 academic year at a secondary school in Almaty, Kazakhstan. The experimental group ( n = 22) participated in STEM–PBL lessons centered on real-world engineering tasks related to the volumes of solids of revolution and supported by digital tools, including GeoGebra 3D, Desmos, Mathigon Polypad, and CalcPlot3D. The control group ( n = 21) received conventional instruction. Prior to the intervention, a needs assessment survey was conducted with all Grade 11 students ( n = 60) to inform the instructional design. Results The survey showed that 61.7% of students favored collaborative and project-based learning and expressed a strong preference for practical and visual learning materials. The experimental group achieved significantly higher mathematical literacy outcomes than the control group (82% vs. 70%, p < 0.001, d = 0.825). The greatest improvements were observed in students' ability to formulate mathematical problems and engage in mathematical reasoning. Students also showed an enhanced ability to identify geometric objects in authentic real-world contexts, decompose complex three-dimensional figures into simpler components, and interpret mathematical results in relation to practical situations. Discussion The findings suggest that STEM–PBL has the potential to foster mathematical literacy in Grade 11 geometry. However, further research with larger and more diverse samples is needed to establish its broader applicability.