There are so many ways decorate a plant pot. Why not paint it with good old puff paint like here (puff paint can look pretty classy - are you surprised?), mod podge magazine clippings or photos, spray paint it with stickers to make polka dots like here, or anything else you come up with.
I think this would be fun for a teacher. Your child can do the decorating, you can include a plant (or seeds) with a tag that says "Thanks for helping me grow!"