We had the conversation hearts, and the cute little Valentine cards like the kid in a car: “You Auto Be My Valentine.” 
Things haven’t changed…4th grader came home with all of the above.
Of course if you are in a religious based school, st. Valentine is a no-no.
I went to a Catholic school and we certainly had valentines.
StG
Mid 60s, public school in San Francisco. We purchased bulk valentine’s cards at Woolworth and gave one to every person in the class. I don’t remember if this was same sex too, and I don’t know if it was school policy or my mother’s. I do remember that most kids, if not all, were doing the exact same thing.
The closest I did to that was at the end of the school year, as a high-school sophomore, in Drivers’ Ed, when, with the teacher’s permission, I passed out bubble gum to everyone in class. Well, almost everyone, because a few turned me down. Remarkable.
Rather than decorating boxes, we made large red & pink hearts out of construction paper, two thickness taped together along the straight sides of the hearts and a handle across the buttcrack at the top. It started out that we gave a card to every kid in class, no candy; around 3rd grade, the guys didn’t have to give cards to guys if they didn’t want to, but the girls mostly still gave cards to everybody. By 6th grade, I don’t think I was getting any cards any more.
Same as a lot of others here. K-6 decorated box, gave one to everyone in your class, got one from everyone.
In junior high (7-8-9) you wouldn’t be caught dead giving or getting valentines. Just wasn’t cool.
In high school dating couples might exchange valentines, but heaven help you if you were a guy and your buddies found out.
Every year in elementary, with at least one year doing the whole “have to give to every kid or no one” thing that’s for some reason controversial lately, then nothing other than “candygrams” in jr & sr high.
If you don’t know what a candygram is, some club or something collects a quarter or dollar or something like that then at some point in the day they deliver a heart made out of construction paper (which you’ve signed, or not if it’s a secret admirer thing) with a hershey’s kiss taped to it to whoever you’ve chosen. I think it was mainly cheerleaders sending them to the basketball players just as a GO TEAM thing, not like a I love you thing.
Remember? Mom kept all our Valentine’s cards in repurposed photo albums!