When I was in Middle school, well just in 6th grade, I had about 7 referrals. 3 for fighting, 2 for profanity,1 for having a controlled substance of marijuana on school campus, and 1 for allegedly threatening someone. I remember them all because 6th grade was the first and last year that I got referrals. I also had social media at a young age. I was very immature. I would post and publicly say things that no 11/12 year old should be posting/saying. Academically, though, I was and still am doing great. I was a straight-A student since Kindergarten. My grades are still high. Harvard has been a dream of mine since 1st grade, But I am worried that my 6th grade behavior will affect my chances of getting into Harvard.
Delete that old social media stuff. Otherwise, none of it matters and nobody cares about what you were like in middle school, @tovar123
^ but also don’t get hung up on Harvard and find a good range of schools to apply to.
I think it will affect your chances of getting into Harvard, but not for the reasons you think. No, Harvard isn’t likely to see or hear of your old social media posts or drug use. Harvard is, however, leading the charge to look for ways to consider character and kindness in admission decisions. And as they say, “A leopard doesn’t change it’s spots.” Your classmates haven’t forgotten your cruelty or your behavior. You don’t sound like someone most high achieving kids want in their study group. Your effectiveness on teams is compromised because they will have lingering trust issues. I’m not saying it won’t happen -you might win an Olympiad, who knows? But I think fighting your “short fuse” is likely to make it a steep uphill battle.
I think you’re putting WAY too much energy into this. This isn’t a top secret clearance. It’s a university. Harvard gets 40,000 applications a year. They literally don’t have time to go searching through people’s Facebook accounts to see if you have a history of stuff at 11 years old. My daughter was just outgrowing Barbies at that age. They’re the snootiest college in the country. They can think of PLENTY of reasons to turn you down for admissions, don’t worry 
We aren’t leopards. Humans can and do change. OP’s chances rest on who she has become.
And that includes being savvy enough to research what H ane that tier fo look for, not wild assumptions like 6th grade behavior. Skip this understanding and how will you present a solid application? Know what matters.
Congratulations on growing from your past behavior.
Honestly, I wouldn’t worry about your 6th grade behavior. Just as many CC moderators and members have pointed ou, on other threads (including my own ones) what you accomplished or didn’t accomplish (including bad bahavior:)) in middle school is for the most part irrelevant. Please don’t spend anymore energy on worrying about this. All is good and if you are a senior good luck with your college apps!