(As usual with my 'school in Finland' posts, these thoughts are based on my own experiences with my own two kids at one school, plus anecdotal stuff I've heard from students and friends.)
I happen to think that the sex education I got in school in the US was perfectly adequate. There was all the usual elementary school stuff starting in about fifth grade, then the heavier stuff during two years of high school (freshman and sophomore year, maybe?). My sophomore year of health in particular was really well done: good job, Mr. Kehoe! We learned alllllllll about birth control. Like, ALL of the things about it. Most of what I have knocking around in the back of my mind about various forms of birth control to this day still stems from that class...and most of it is still completely accurate! Needless to say, this was not an abstinence-only program, though abstinence was presented as an obvious form of birth control.
I mention my own background with sex ed because I know that sex ed varies extremely widely among states, cities, and even schools. I don't know if my elementary or high school sex ed programs were opt-in, or opt-out, but as I said, I feel like I learned what I needed to know.
In my experience as a parent here in Finland, sex ed started a bit earlier than I expected. Magdalena started learning about sex from a science/biology perspective in second grade. They learned about sperm and eggs and watched a video that is very similar to one I watched in high school health class (it's the one with the actual footage of sperm doing its thing).
I haven't heard a lot about what Miriam is learning (she's less effusive than her sister about everyday goings-on in class - Magdalena is the kind of kid who can walk in the door and say "hey, Mama, look at this video we watched about sperm!" and Miriam is...not). But I do know they've had talks about periods and puberty. They even sent all the girls home with some pantyliners and such.
Here's where it gets really interesting, though: sometime around eighth grade, students can go to the school nurse and get birth control, for free, without their parents knowing. This is more than just an anonymous drawer of condoms that they can dip into - it can be actual birth control pills. Is this a thing in the US? If not, do you think it should be?
Because the thing is, I think this is maybe not the most horrible dea. It's one of those times where your "if the world was perfect" ideals run into your "but with what things are really like..." ones. In an ideal world, my daughter (or anyone else's) would talk to her mom and dad about birth control (or, even more ideally, not NEED to, but you know) and obtain it under their guidance during some kind of lovely joint doctor appointment where all the options and consequences are carefully explained.
But in reality, if my kid doesn't want to talk to me about it, and is going to do those things anyway, I would rather she have access to birth control than not have it. I know that back in my day, there was talk of "if you teach kids about birth control, they will be more likely to have sex." But I seem to recall that we have now decided that it's more like, "if you teach kids about birth control, they will be more likely to use birth control if/when they have sex." Right?