Is there a reason your grades are slipping? Are you having a hard time understanding the material? Do you just not have enough time to study because of everything else? I think you should see if you can talk to one of your teachers or your therapist and see if someone would talk to your parents on your behalf. It sounds like they may not listen if it comes from you, but if your t or your teacher explains to them how hard you are trying but that you just have too many things to juggle, they might be more understanding.