Year 10/Year 11 GCSEs or IGCSEs approx 8-11 subjects usually (15-16 year old) sometimes up to 18 if you're unlucky.

(I)GCSEs stand for (International) General Certificate in Secondary Education.

Year 12 AS Level (Advanced subsidiary Level) 3-5 Subjects usually (Usually 16+ years unless you are a genius)

Year 13 A2 Level (Advanced 2 Level) 3-5 subjects

All subjects can be retaken to get a better mark.

If you complete AS & A2 in any subject you get an A-Level

Hope that helps!