monoprint hearts for your sweeties

 Coinciding with a math lesson on symmetry, on Valentine's Day. I mean, how does it get better than that?

 Tempra paint, oak tag half hearts, paint bushes, construction paper, crayons.
Only trouble was that the paint dried very quickly and some of the students found themselves with a monoprint that was less than desirable - also, avoid words, like our friend in the top left.  And a final word, for the sake of expediency, consider pre-picking the color of the paper and pre tracing the hearts. If there's time to kill, make them do it. If time will likely be an issue, mandatorily hand them a pretraced half shape and say "paint inside the lines". In this case, it doesn't stifle their creativity.