What should I do if I realize my high-school mathematics foundation is weaker than my classmates’?

First, consult the course instructor or an academic adviser early and identify which topics you need to strengthen. Then prioritize the mathematics required for your courses, review it using textbooks or high-school materials, and practice consistently, even in short sessions. If available, use remedial classes, question sessions, learning support, or tutoring, and avoid leaving unclear points unresolved.