Sex education? Not in the sense of the kids watching porn, but learning about contraception and STIs and that kind of thing.

fair enough but is that really the reason edtech has failed?

IMO, EdTech has failed because it's BS. I'd sooner buy GameStop stock than the next EdTech-in-schools startup. (EdX, Khan etc. are playing in a different market, and doing ok.)

But sex ed and the like is definitely something that gets parents upset, as is the general concept of "they're teaching my child things they're not telling me about", whether that's critical theory, sex ed, evolution, or anything with the word gender in it.

This is a problem that has been around for years, perhaps decades. One memorable example comes from "To Kill a Mockingbird", where the teacher complained about the main character Scout having learned to read before her 1st grade -- when Atticus had nothing to do with it, because she learned how to read on her own at the age of 4.

Others have given their own experiences in this thread -- some teachers are encouraging, others get frustrated.