Giftcards, and a book signed by my child to the teachers classroom. Sometimes we will give a toy for the classroom if the teacher doesn't have good indoor recess games. I like to give books the kids like to give the toys.

Don't forget the school secretary she gets all the hard work and nobody recgonizes it. She is the one who calls when your child is getting sick on her floor. Eveyone remembers the principal but not the secretary. just a thought