I will try to explain most education systems! Till you’re 16, you generally work towards your G.C.S.E’s. These are for your secondary education after primary school. You do your SAT’s when you’re about 11/12, but those aren’t important to know in detail if you’re 17. After G.C.S.E’s, you go on to do your A Levels, which are divided into two halves now. You do your AS Level first, then your A Level. This is to give you a qualification even if you finish after one year. After this, people go on to University. This isn’t the only way to get to University, but it’s what most school leavers do.

I hope this helps!