Possibly MrMan - but I think the converse is more likely.
I'm not a parent but I'll answer anyway
I've noticed this openly gay thing amongst younger people since around the mid 90s and I think it's great.
I think teenagers in general are less inhibited than they were in my day anyway (lad).
They are also more optimistic about options open to them in life and less concerned about convention - even within their own subcultures. E.g. an "Emo" kid might think nothing of letting it be known that he is mad into football even though it's 'against the rules' as it were. A full on metal girl might like sewing and cups of tea - and wouldn't care who knows it.
In my time we were all much more circumspect about these things. Sexuality these days is as mundane as which beer you prefer - and I for one am glad.
Of course yes, there is an element of "oh aren't we shocking" but I think it's the minority. Teenagers eh?
I'm waiting for the day that to stand out and make a statement, kids are going to wantonly display the fact that they
don't have tattoos/piercings etc, are into the most conventional 'musak' around, and are fiercely straight.