I am a headteacher of a small village school in the shire counties and we have a strong push on equalities in all areas (as we are almost exclusively white monocultural). We talk to the children about difference (eg racial, religious, physical ability, academic, family make-up, sex, sexuality) from the moment they walk through the door. It is very rare that anybody has any issues with it, as it is merely drawing the children's attention to different features about the world we live in. We do not encourage the children to be a different race, or to believe a certain religion, or to consider themselves blind, or to choose a particular sexuality, but we do encourage them to consider what life is like for people with all these differences. We draw their attention to the fact that Hitler targeted gay people and the Gypsy/Roma community as well as Jews, and consider how 'othering' people can lead to division and mistrust. As a Church of England school, we draw people's attention to the teaching of the church (Valuing All God's Children) which is that all are loved and equally valued and that everybody has a responsibility to challenge homophobic, biphobic and transphobic bullying and prejudice. As far as I am aware, we have not converted anybody to become gay, or Gypsy/Roma, or a certain religion, or disabled. My gay brother, on the other hand, has said that despite having Baywatch and a straight culture pushed down his throat for years, he still 'chose' the gay life, which rather negates the fear that exposure to something automatically leads you to take it on.
I do sometimes get parents with concerns and try to meet them where they are at in their thought processes, as concerns are usually through ignorance. On the rare occasions I am met with a brick wall, I suggest they transfer their child to the madrasa school in the local city, as they will get a gay-free education there.
OP, I suggest you talk to the school to find out exactly what is likely to be taught, and also try to get your concerns clear in your own mind. You might be pleasantly surprised.