hello there, i know it's a lot to ask of second grade, but make sure they
press really hard with the crayons or it doesn't really work that good. Also
if you paint on india ink for them later or while they watch, it is so fun
and works great. We recreated Starry Night by Van Gogh with white crayon and
it was a mystery to them until we painted on blue/black ink. They loved it.
Kinda like invisible drawings/ mystery paintings. Good luck.