I was not a mean child though I definitely had outdated beliefs that my kids don't seem to have. I don't know how much of that is that I grew up in Tennessee in the 90s.
I played with everyone, but I was also a wimp so until recently I never would've been one to step up to defend someone. Often I wouldn't have known that what they were saying was necessarily bad or wrong.
I didn't realize until middle school that interracial marriage was a thing. I didn't have much awareness of gay people until middle school either. I grew up in areas that were largely white so for a long time I believed the sugar-coated, incorrect versions of American history. Until adulthood my only real knowledge of trans people was them being made fun of on TV shows. So while I'm still not perfect I believe I'm a better person now.