I brought it back to intercourse because you posted this
The definition of adults having sex is "intercourse".
I know child development from 2 sources. One is my education. Nursing school requires a basic child development course and a child psychology course; my Patient Education certification additionally required the child development courses that teachers take. And because of my personal interest in the subject I took a more advanced course as an elective. I'd never assume that any of those professors were childless as you did.
Another source is being the parent of 3 kids, one of whom was developmentally delayed until age 10 because of her premature birth. I worked very closely with developmental pediatricians and psychologists for many years for her. All my kids attended kindergarten (2 in private Christian schools, one in public school) and amazingly, all those curriculums were age appropriate! That was never a concern for me. And in the countless parent orientations I have attended in the last 19 years I have NEVER heard a single parent bring up a concern about the age appropriateness of the curriculums. From what I read in the OP, I still have no concern that suddenly out of the blue, the curriculums are going to make a total turn around to teach age inappropriate content on a controversial subject that strikes obvious terror into the brains of so many. Why are you worried about that? Have you had other experiences where your kids have been taught age inappropriate material?