If there are any papers and homework that need parents' signature before, you can find them, then find a blank piece of paper and imitate them several times according to parents' handwriting. It's easier to choose an ugly imitation.

By the way, do you go to school by yourself or do your parents drive you in the morning? The latter two are easier to handle, provided that the other one is not suspicious, you can fold the paper, and the one with less marks is best kept for parents to sign (I have done these methods, the first one is endorsement ...) I hope it will help you:)