If your grades go back up and your parents back off, smoke in moderation until you are out of the house. Weekends, holidays, never in your parents' house. Smoke outside, in a car, someone else's house, etc.

Going clean for an extended period of time can be a test for anyone, but you learn to replace it with other activities. When you smoke that first time after not smoking, make sure you won't see you until much later.

Find a reliable friend that doesn't do anything to pee in cup for you if they decide to piss test you.

Just be smart, and respectful of your folks. They don't trust you right now, you need to focus on regaining that trust before you can safely lie to them again. Don't smoke in their house, don't smoke when you know you will be seeing them shortly after smoking.

oh yeah, Target and a bunch of stores like that often have little travel size Axe spray for like a buck. Carry one of those in your car or on you. I've found that Axe covers the scent of weed pretty well.

Peace

Good luck