A good starting point is to review the UK Government's guidance on how long you need to stay in education, they say:

"You can leave school on the last Friday in June if you’ll be 16 by the end of the summer holidays.

You must then do one of the following until you’re 18:

• Stay in full-time education, for example at a college

• Start an apprenticeship or traineeship

• Spend 20 hours or more a week working or volunteering, while in part-time education or training"

This is for students studying in England.