In elementary school? Excessive flatulence.

In middle school? Generally smelling bad and poor hygiene (thanks parents)

In high school? Well I started showering so not nearly as much. Although I am the reason why they take all programming tests on paper now. They had generated online tests/quizzes on some webpage that used Javascript to "encrypt" the answer set and I do use the term loosely as it was mild obfuscation at best. It eventually calculated your score and then submitted some form that sent an email with your grade to the teacher. I inserted some extra code to print out the answer key at the bottom of the page in white font. I would highlight it when the teacher wasn't around and then click off of it when they were. I sold it to some people until word finally got out but nobody ratted me out in particular. It actually came back to bite me in the ass because there was a mistake in the key and I changed one of my answers to the wrong one on purpose, but then she corrected the key later. I couldn't say anything for obvious reasons.