Yeah I didn't learn about any sort of Sex Ed at school until 10-11, and it was mainly things like bodily functions and care (also separated lessons by gender). I think we were 14 or 15 before they actually got into the nifty gritty of "one day you'll have sex, use protection or get an STI or baby" until I was 14 or 15.
I don't think that's unreasonable.
Also on the whole "what will I tell my students about...": good gosh, I don't recall talking to ANY of my K-6 teachers about their personal lives, and usually it was a general "we did [x]" or were anecdotes about something that happened solely to them.
And this is in a small town where the parents would certainly already hear rumours externally if Mr Smith was into BDSM or booked an excess of prostate exams.