Is it legal to work full time under 18?

I'm 16 and my mom searched my room and there was a bottle of captain morgan in the drawer under my bed. You can call me stupid for having it, I know drinking underage is a crime, but I've drank like 3 times and since 80% of kids in high school have, I don't think it's a HUGE deal. Anyway my mom said it was the last straw and I either had to work full time (8-6 every day but sunday) with my stepdad for the rest of the summer, or move to my grandmothers without being able to hang out with anyone that lives around here. Anyways I chose my grandmothers but is working over 40 hours a week at 16 legal anyway?