75 year old me to 15 year old me
60 years changes you.
In high school, that boy doesn't matter. How you look doesn't matter and nobody really cares how you look or sound.
Be nice to your parents and listen to what they say. They do have some knowledge. Don't ask for everything, you really don't need all of it.
If you believe in something, speak up. You do know some stuff too and are pretty intelligent. Like with the gun control, do research and spread the word about what you learned. People will listen eventually, you just have to have a loud enough voice.
Whatever college you go to will be fun, and you don't need to have an A+ in every class. Don't take 8 am classes or classes that only meet once a week. Do take classes that are pass/fail. Make it an easyish class that you know some of the information already.
Don't do a major because your parents tell you too. Major in something that you are passionate about. Start saving money, because your parents won't be there to give you everything. Get a job to make money.
Fall in love, talk to that guy in the coffee shop. Be crazy, live how you want to. Life is an adventure, and so is the time after. Get fired, no one is perfect. Everything will be fine and you will always be alright.
Live life and nearly every mistake is fixable. Do not hurt or kill yourself. Everything gets better. Live laugh and love.