Below is an excerpt from a 1898 publication: School Education Vol.17. This probably isn't something one would think about when picturing Valentine Celebrations during the 19th century but I felt it is kinda fun to see what School teachers were encouraged to do.
ST. VALENTINE'S DAY, FEB. 14
If it seems to interrupt the regular work and you are tempted to overlook it, go back into your own childhood for a minute and think whether it is the "regular" days that you remember, or the days in which something a little out of the ordinary happened. Tell the legend of St. Valentine, and that it is love that makes the tokens valuable. Nobody wishes to send his love with anything that is not pretty, of course, so the question of comic valentines is easily disposed of.
Now we will make some valentines to take home, and mamma shall be the recipient of these favors. Sketch a dainty flower on a small card and have the children color it with colored pencils or with water color. A bird with a letter in his mouth is a pretty design to be perforated or sewed, while a heart sewed in red worsted, or cut from red paper and pasted on a white card, is effective with an appropriate motto. Always choose some simple design. The result will be much more satisfactory when completed than an elaborate affair, for the latter will be only half done, and so soiled that neither' giver nor receiver will find much pleasure in it, except as an expression of love.
Let envelopes be made and the "love tokens" taken home to be put at mamma's plate or to be left at the door with a loud ringing of the door bell.