There's also all the stress of living alone at that age: Cooking, cleaning looking after yourself, full time college, homework, revision. Near exams you need people who will take care of you and ensure you eat properly and revise enough but not too much ( I take it you're approaching A levels or A2s). And if you want a social life on top of that? There's also the problem of your baby sitting, would just moving out really be enough to get you out of that duty. Alternatively as if you weren't there your parents would have to pay a babysitter and so that entitles you to a payment you could say and save some money that way. But really as much as you want to move out it would probably be for the best to remain put for a while, till you're 18.
That doesn't mean you just have to put up with it though. If you explain your dilemma to your parents and try to find some sort of compromise, and if you can't reach that then just say you'll get yourself a job on Saturdays whether your parents like it or not, then they have to either agree to your compromise, independence or pay you for babysitting as that is the reason you cannot get a job.