As the parent of a almost 15 year old girl I'm naturally worried about this issue. Teenagers respond best if they are treated as adult and the idea that you can unduely influence them just by telling them about homosexuality is absurb. In fact it will greatly help them to meet well balance people of all types. I am convinced that the way to teach sex education is to bring in people who are only slighly older to relate their experience, how their decisions have affected their lives and how they have handled things.
Meanwhile I deal with my daughter's impending adulthood with the strategy of keeping her busy with music , dancing and homework, trying to raise her aspirations for the future and by making her listen to my entire collection of songs of women who have surrendered their maidenhead and regretted it. I can very nearly accept her as an adult but it is difficult. ( I've gone off the point - sorry )