Ron. W: Dating non witness schoolmates.
I would even say "dating witness schoolmates." Though that wasn't quite set in stone. My recollection is that JWs see dating as the first step towards marriage and not as some fun fling that kids do as they enter adolescence. Dating was frowned upon for anyone not in their late teens (and for some parents, dating was not for anyone in their teens at all).
Many JW parents were also fanatical about music or other media. I remember being teased at school because I wasn't allowed to watch a Bond film on TV (The Spy Who Loved Me, if I recall correctly) because it had the "Parental Discretion Advised" warning. And this was network TV, where movies were heavily censored to appeal to exactly that sort of parent.
And of course, not being allowed to salute the flag or recite the national anthem. While I do not care for these activities being forced on children in school, it was yet another way to differentiate ourselves in an environment where it was already difficult to fit in. I was fortunate that I usually had one or two other JW classmates to share the misery with. But we had to either sit at our desk while everyone else stood, or leave the room and wait in the hallway. Not very fun.