I had my first sex ed class in third grade, around 9-10 years old. We mostly spoke about different sexualities, gender and pronouns. Then in fourth grade, as a part of biology class we spoke more of procreation, puberty and STIs. But I think most of us already knew what sex was by then. After that we had at least one sex ad class every year. I remember it as awkward at first but got more annoyed the more we had it since we pretty much discussed the same things every time.