Tell a teacher that you trust or a coach or a pastor. Don't let anything discourage you. Stick to your guns. Do you have an aunt or uncle or cousin who lives close you can trust? Always remember you are not responsible. You didn't do anything to deserve it
Go to school guidance counselor.Have them contact a representative for Child Protective Services in your county.A representative will come to your school and interview you,free from your parents so you can clearly tell them what is going on.Then they will tell you what comes next.They will get the proper help for your mother.There is no excuse for abusing a child,so if she thinks there is,they will set her straight,and your father too.These people are professionals.They have heard every lie someone can tell,and they will believe you.Good luck.Tomorrow is not too soon.
Read and follow Kitty Susca's advice, seems smart way to handle a touchy situation. not sure how often this happens or if is just now starting so eventhough my first reaction was Cops, it may work out better having adults involved determining what the best way of handling could be. but DO NOT wait please, get advice ASAP!
With your dad not doing anything about it makes me wonder if you're just being spanked - not hit which would show bruises and welps. What are you doing to provoke it? Are you out of control? Just need more info for sound advice.