I actually did this, apologized to someone from middle school this year and I'm 25. I remember her having issues and self harming, and I don't remember exactly what I did, but basically suggested she wanted attention (she was really pretty and well liked and I was jealous.) In the end all of our friends saw me for the asshole I was and most excluded me, but it bothered me more and more over the years, and eventually I reached out.

She took it very kindly and basically said she hardly remember because it was kid stuff but that she appreciated it.

I think high school is more memorable. To be honest, if any of the girls who bullied me during grade school or even high school (it happened often, I was always the odd one out) reached out and apologized to me, it would probably give me allot of peace even if I found it weird. I don't see it causing more damage or hurting more.

So I guess I can see both sides of this. Being in friend groups and never being invited, often excluded from activities, honestly still hurts me now. Those are important years. I would reach out and say something. Can't hurt.