I want to verify for myself that I _know_ the material. A series of challenging exams will do that more thoroughly than completing exercises from a textbook or online course (where, let’s be honest, we’re more forgiving of ourselves than we should be).

Check out Barbara Oakley’s Coursera course called Learning How To Learn. It turns out exams are actually an excellent tool for learning, more so than learning without assessment.

A side effect has been that having a deadline and a measurable outcome has been incredibly motivating. I’d have probably been distracted by side projects if I hadn’t committed to the exams.

And yes, it’s accepted for uni entrance here. STEM courses at top unis will expect A-level grades in maths/science subjects, even for mature students with industry experience.