I have the kids write their teacher's name , e.g. "M is for Mrs. McKinney" and sign it.
This year we had a handful of "m" teacher's to thank!
I use an exacto knife to trim the crayons and a hot glue gun to secure them to the paper. I let the kids arrange them on the page in the color order they desire. They write a hand written thank you note to accompany the gift.
What do you do for end of the year favors? There are so many great ideas on pinterest. Please share some of your favorites!