I think it's okay for young children to be taught about the existence of LGBT people, just as it's okay for Christians to learn about Muslims or vice versa. There shouldn't be anything sexual about what they're learning until sex ed. I will say that I was 10 when I first had sex ed (5th grade), which is a normal age to start learning about that kind of thing in many areas. Either way, if the kid can be excused, he should be allowed to and should not be suspended for that. That was very clearly the wrong decision in my opinion.