Our student council came up with the idea of making green, peppermint milkshakes for St. Patrick's Day, which we did over a Friday noon hour. It was a hit, and sadly we didn't buy enough supplies and sold out before the next class started. Just make sure you have enough blenders and also, do a test run a few days before to figure out how much milk and ice cream you need (we had two cups of milk and filled almost the rest with ice cream which filled three cups. We sold them for $1, but looking back could have sold them for more).
This is a fun activity for the students and can be done for any holiday or just during a slow month.
Medicine Hat, Alberta