Skipping class tomorrow?

Ok so I'm gonna skip math and go to the beach with some friends. The problem is that the school has this think I like to call auto narc. The call home and tell your parents what class you missed. Should I tell my mom I skipped when I get home or just sort of let unfold? Would it serve me less punishment if I tell my mom straight up or should I say that we watched another bad movie in planning so I left? I know this is kinda stupid to be asking but my parents are kinda strict and I'm tired of it.