It's sod's law, but parents never think theyr kids work hard enough. There is always that little more effort that needs to be put in. Or that one more essay to write. Or things are just not to the standard their offspring are capable of. It's sod's law.
Are they refusing to let you out at the weekends? Or just weekdays?
Hun, don't give in. Put the knife away. Busy yourself with something, maybe painting or reading or playing a game. Or chatting with people on here.