Teacher's do get buried under all the gifts. A small token is good or something pratical.
An ornament with the child's name and year that way it doesn't have to match anything. It would be cute if it is a favorite teacher to print the child's picture on one side too.
A "grocery bag"....it could be quilted or just a heavy fabric to encourage "going green". They are a big thing around here now with the grocery stores doing away with plastic and charging for bags.