I have a dad that might react violently to a report card... help me?

You need to talk with your school counselor about this immediately. You should not live in fear of physical violence. You have a right to live a peaceful life free from that kind of physical or mental abuse. Your father needs help. Your school counselor can help start the process for you and your family to get the help you need. Do not be afraid. Family violence is far more common than you might realize. You're the victim here. Violence is never ok. Ever. Call your counselor RIGHT NOW!