IMO, kids don't need to be taught about alternative sexuality at least until they enter Junior High School. And even then, they shouldn't normalize it. Tell them what it is, what the letters stand for, tell them not to discriminate against those in that community, then keep it moving.
Male, female relationships should still be what's taught to our kids. I have 3 of them, and I'd prefer they be taught that reproduction occurs between a man and a woman because that's how we as humans are designed and created, and that's what's normal. But still, no one should be discriminated against or treated badly regardless of their sexual orientation.