If you don't want your kids learning about something, send them to school with a note that gets them out of that class.
We do it over here all the time.
That would work for me as I've done the same when I'm made aware of controversial topics being discussed. The problem is controversial curriculum like this has a funny way of being a full on program spanning the course of several days or even an entire semester as opposed to traditional sex ed which back in the day consisted of one assembly on one particular day.
In addition, parents aren't always made aware of controversial issues ahead of time. We see it all the time where the damage is done and parents find out only after their children come home and tell them about it. The schools give a limp dick apology and a half baked excuse but as mentioned, the damage is done.