One difference between England and America is that if a pupil does the full course in England (normally to A-level) s/he will finish in 13th grade. My younger children went to an international school in Switzerland and did the
International Baccalaureate instead of A-levels. They still finished at the end of 13th grade. A good IB score will normally allow a student to take a shorter degree course at an American university. English bachelor degree courses normally take only three years.