I wouldn't be suprised if your 17 yr old is smoking pot as well. You need to talk to your kids, talk to your 15 yr old about sex, ask her if she is doing it? Your 12 yr old is going to drop out of school????You need to get a handle on these kids, they sound as though they are walking all over you. Put your foot down, don't let them out of the house so they can't do this step. Good luck