Abstract
This study evaluated the effectiveness of Khan Academy as a supplementary tool in teaching Grade 8 Mathematics at Tabaco National High School during School Year 2025–2026. Using a quasi-experimental pre-test–post-test control group design, 66 students were divided into a control group (traditional instruction) and an experimental group (traditional instruction plus Khan Academy). A validated test aligned with the MELCs served as the research instrument, and the researchers analyzed the data using descriptive statistics and t-tests. Both groups started with low mastery in key algebra competencies, especially factoring, simplifying rational algebraic expressions, and performing operations on rational expressions. After the intervention, both groups improved, but the experimental group showed substantially greater gains. In the post-test, the experimental group reached Full Mastery (92%) in multiplying monomials and binomials, Mastery (75%) in factoring polynomials, and Near Mastery in special products (65%) and simplifying rational expressions (68%). By contrast, the control group achieved only Near Mastery in multiplication (63%) and factoring (54%) and remained at Low Mastery in other areas. Pre-test comparisons showed no significant difference between groups (t = -1.25, p = 0.080), confirming baseline equivalence. Post-test results, however, revealed a significant advantage for the experimental group (mean = 27.45 vs. 19.64; t = -4.80, p = 0.003), indicating that Khan Academy meaningfully enhanced learning outcomes. Despite these gains, performing operations on rational algebraic expressions remained the least mastered skill (30%, Low Mastery) even for the experimental group, underscoring the topic’s complexity. Khan Academy effectively strengthened conceptual and procedural understanding in most Grade 8 algebra competencies but was insufficient alone for the most complex skills. The findings suggest integrating Khan Academy with scaffolded teacher-led instruction, guided practice, and contextual applications to help students achieve higher mastery, particularly in multi-step rational expression operations.