Demand family drug tests (assuming you don't actually do weed elsewhere).

the 1708 people so far who said you deserve it must all be crazy step moms

She reminds me of a step mom I had

I say if mom is still alive and kicking go live with her and tell dad until he realizes you never do such things you will never see him again.

Walk up to you're step mom(when she's alone). Say "Listen, what you did was not cool, and if you do it again, I will take this to the next level." Then punch yourself in the face, right around the eye. Really hard. Maybe a few times. Then say this "Well [insert your teacher's name here], I fell down the stairs...." Pause Then "Tonights news story - [Step mom's name] was arrested today for child abuse."

I'm sure the police would love to get their hands on her

First of all, GET REVENGE. Plant some condoms (THAT LOOK USED) and stuff around, like on the floor, slightly under the couch, etc. Then, start planting cameras EVERYWHERE. Buy a miniature recorder and stick it on yourself. Then get her to confess ("You're a little bitch for planting weed in my room, you know that?!" "Well you shouldn't **** with me"). If all else fails, just go ahead and tell a lot of people. I don't mean a single teacher, I mean tell EVERYONE at school, post it on social media, put flyers up around town, etc. Not only will that ruin her reputation, but the pressure of everyone knowing will make her crack.

Plant used condoms in her room.

Install cameras in your room, like some of those nanny cameras. That way you can show your dad she's lying and to trust you more.

Just end up smoking it... Lol