You just tell your kid not to do anything that makes them the least bit uncomfortable and back them up and let the school know that your kid has the right to refuse to do anything they don’t want to do regarding sex education.
And that is exactly how I handled government schools when mine was a kid. I got a Vice Principal fired once because I raised so much heck. Started with her and went straight up the ladder to the top. A month later she was gone.
My daughter got suspended for a week under their ‘rules’. I told her and them that was fine if that was the rule but what followed after was completely unacceptable. I never let teachers/admin, etc. intimidate me. They were no better or smarter in my view and I would tell them so. I also could back it up with a much more rigorous education than they had. They backed up pretty quick when I walked in.