I am a teacher as well. I agree with everyone else on gift cards. I love to get gift cards. I don't expect to recieve anything but I'm always appreciative when I do. I love hearing thank yous and kind words of appreciation the most!!!
This year for my son's Kindergarten teacher, my son and I are giving her a "giving tree" along with a copy of Shel Silverstein's book "The Giving Tree". The book is based on a boy who wishes and needs something throughout his childhood and the giving tree provides for the boy throughout his life, much like a teacher gives and devotes his/her talents and time to children/teens. I bought a small Christmas tree and hung gift certificates on the tree from various dining places, bookstores, local teacher supply stores, and Wal Mart. Books-a-Million even carries a gift card with the picture from the cover of "The Giving Tree" book. I also hung teacher ornaments that I bough on sale a while back at our local Hobby Lobby store. I also found at Hallmark a black chalkboard with Dear Santa, at the top. I added, "please be good to our teacher". This gift can be as inexpensive or as expensive as you would like. Hope this helps!!