Your description of the 1970’s health education is pretty accurate except in my upstate NY school, they did acknowledge the existence of homosexuals, transvestites, and transexuals, without politicizing the conversation or advocating for the lifestyle. In my school, the health teachers were mostly coaches and a drivers education teacher.
The only controversy that I can recall was when a nurse from planned baby killing spoke to the class about birth control once a year. Students were not allowed to attend the class unless a parent signed a permission slip. Most of us used this as an excuse to skip the class.
My memory is a little foggy on the details, so I can’t confirm whether Planned Barrenhood paid a visit. I do know that the guys were split into a separate class from the girls for the sexual portion of the health class, for obvious physiological differences. They may have heard from the abortion “nurse,” but being the late 70’s, I doubt it.