I regret not putting more effort in, I have just recently realized how stuffty the brains of others are when it comes to testing. Usually, I'll get an A or B on a test without studying, while someone who spent an hour the previous day studying will struggle to get a C. I put almost no effort into any of my school work, leading to passing each grade by increasingly smaller amounts. I passed 8th grade by ONE point on my science final.
I also regret not taking the many opportunities that have presented themselves to me. Social or otherwise, I'm always too hesitant to take an opportunity.
I also don't understand how some schools say that making a finger gun is a threatening expression. I've seen a few people get detentions for doing so.