I too, in first grade had pretty much the same exact scenario! The door couldn’t be locked and a boy bust in while I was pooping (it was the boys bathroom) and did a “point and laugh”. Traumatizing and I don’t think I ever pooped at school again

Edit: Now that I’m grown, I find it fun to fart while using a public urinal. You sometimes get chuckles, but rarely does anyone risk making eye contact with anyone using a urinal