Not sure if this counts since it wasn't done as a teenager, but most of my shenanigans were in undergrad.
The Drop Card:
I was on the 10-week quarter system in college, and most classes would allow you to drop by the end of week 2 without a penalty with a signature from the professor or TA. After week 2, you'd have to get a signature from the professor. After the end of week 5, no dropping unless you get a signature from the dean of that particular department of education. Usually this is only reserved for extenuating circumstances. At the end of week 6, drops become impossible - the system just doesn't let you.
So I'm in a class that I just bombed a midterm on and I really just don't get the material and don't like the class. It's near the end of week 6, so my only option is to go to the dean if I want to drop. The dean knows me from some of the extracurriculars I'm in and he'd know that I won't have an "extenuating circumstance" - not to mention he's kind of an asshole altogether and probably wouldn't sign my drop card anyway even if I could make something up.
Lo and behold, I find out that one of my friends has an old, expired drop card that he never submitted, with the dean's signature on it. I take the card and pore over it, literally, for hours. I know that he always signs using blue felt-tip sharpies, so I go out to Staples and buy a blue felt-tip sharpie for this one exact purpose. I go through pages and pages and pages of mimicking that exact signature before picking up a stack of drop cards and signing a bunch of them with the same signature.
I pick the best one, fill it out, and turn it in right before the Registrar's office closed on the last day of week 6. Mind you this is a dean's signature so it's actually well-recognized. Lady takes the card, gives me the dropped class receipt and I'm on my merry way.
The Final:
How do you discourage cheating? You make an exam short-answer / essay instead of multiple choice, and require your students to take the exam in class.
How did we get around it? In big lecture halls at universities, it's impossible to keep students spread out to stop them from looking over someone's shoulder - all the seats are right next to each other and the students are packed in. So we had a friend who had taken the class before and done really well in it come into the final with us. He was not enrolled in the class. He goes through the questions and writes in LARGE lettering on the sides of his blue book for us to see the keywords we need to hit for each question.
We turn in our final exams as we finish and get out of there. He waits until the end of the final, when 100+ students are lining up to hand in their exams, when he just slips the blue book into his backpack and casually walks out amidst the chaos.
