Here's a great craft activity for you to try with your class on St. Valentine's - it's called a Valentine's Streamer and it's basically a hanging string with the separate letters that make up the 'Happy (heart) Day' phrase. This awesome 6-page craft worksheet was kindly provided by Hallmark, can be also downloaded from their website, and features their all-time favorites: Hoops and Yoyo.
Here's the set of instructions:
Cut out shapes along solid lines,
fold in half along dotted lines,
arrange shapes to spell 'Happy Valentine's Day',
insert ribbon or string at folds,
tape or glue pieces closed if you want,
hang it up and smile!
Happy St. Valentine's Day to you and your class, hope you enjoy this day with this amazing worksheet!