The issue is you're making an issue of sex when it isn't about that. The new curriculum is literally just about teaching kids that some families aren't the typical 1 mum and 1 dad, and that it is possible to have 2 mums or 2 dads, and that this is perfectly normal and OK. Quite why people feel the need to protest outside a school and withdraw their kids from education is beyond me. And getting back to the initial point, it is nothing more than homophobia from religious zealots.
I'd get the outrage if, like
@Eyepopper says, they were being taught about anal fisting, but they're not. It is literally nothing to do with sex. And I think this is where a lot of the issue has arisen because people are confusing themselves between two different aspects of the curriculum.