|2015 Candy Hearts from the Atlantic article|
The centerpiece of the class Valentine party in my schooldays was a decorated Valentine box made of a cardboard hat box (something that doesn't exist any more). The box had a slot cut in the top, and everyone would put in personally addressed Valentines, which were distributed during the party. Besides the chalky hearts we had lots of home-made cookies.
I think classroom celebrations are still pretty much the same now except the kids probably decorate a box from amazon.com -- hat boxes being even more obsolete than the hats that were sold in them. Also, in some parts of the country, sweets aren't allowed at school parties, so I guess they can't have candy hearts or homemade cookies either.
I looked up the history of Valentine customs in England in Ronald Hutton's definitive book Stations of the Sun, A History of the Ritual Year in Britain. The earliest Valentine traditions weren't about human lovers, but about birds, who in Chaucer's time were believed to pick their mates on Valentine's Day. Sweet!
For a long time, people picked someone to be their Valentine, but the choice was made randomly. Beginning in the mid-18th century, children in some parts of England went from house to house asking for treats, much like the Halloween custom.
Rhymes like this became part of the tradition: in the morning, children would say the rhymes and receive presents from their families. In some places in the 19th century, the presents were given by "the Valentine Man" or "Father Valentine" an anonymous figure who left "sweets, fruit, pencils, or a book for each child on a window-sill or inside a hallway." (Hutton, p. 149)Morrow, morrow, Valentine,I'll be yours if you'll be mine,Please to give me a Valentine.
Valentine cards became extremely popular in the early 19th century, with the post offices handling traffic far in excess of every-day demand. Towards the end of the century, "mocking, insulting, or 'indecent' Valentines" became popular, driving the more romantic and pretty cards out of favor. By 1914 the tradition of sending cards almost died out, but was revived in the 1920s with influence from America, and Valentine cards have remained popular in England ever since, according to Hutton.
Oh, and the New York Times, in an article in "The Upshot" says that those chalky hearts are "3,777 percent more likely than normal" to be eaten on Valentine's Day than any other day of the year. Champagne, oysters, strawberries, and many things dipped in chocolate are also consumed in larger-than-usual quantities. Sounds good to me. I hope you enjoy your celebration.