basically, in Primary School there's infants and juniors. in junior school we do sats or cats depending on the school. this can be what gets you into a preferred secondary school. Secondary school starts at 11 and goes till you're 18. In year 9, (13-14) you choose what courses you wanna take for your GCSE's (or IGCSE's which is what im taking) and english lit and language, maths, one, two or three sciences and a language is mandatory. Then you can choose whatever your school offers until you have 11 which is the max. Your GCSE's is what counts towards college and university. College is part of secondary school, its for 16-18 year olds and can also be referred to as year 12 and 13. You do GCSE's throughout Year 10 and Year 11. Then, in college, you choose your A levels and AS levels. This is what really counts. You choose 2 or 3 depending on what you wanna do at university.
Hope this helps explain the UK school system xD...
(british people correct me if im wrong bc my school is odd)