As a daycare teacher(and we get all kinds of gifts), I've seen/been given...
1. notepads/nice pens-teachers write a lot..if you shop the Dollar Tree, Michaels, Target in their dollar sections, you can get a lot of fun sized/shaped notepads
2. giftcard to the school supply store in our town-teachers spend a lot out of pocket and this might help her get her classroom ready for the next year
3. giftcard to Target-get lots of stuff in the dollar spot
4. If you do a tote bag with handprints on it-make sure you seal the handprints or the first time it gets wet, you'll have it running all over the place in a big mess
5. Do a book...take a picture of each kid, find a cute school poem, put the poem on one sheet of paper and then have the child's photo on the other and have the kid write what they liked about school this year, bind them together, and make a book. You can have the kids write what they liked about school this year and pull them one at a time to take phots. Keeps the rest of the kids working while you pull them one at a time to take their photo. Make sure you give them prompts of ideas to keep them on task
-what fun projects did we do this year
-what books did you like reading
-what was your favorite subject
-who are your friends
Make sure you make a block or square where the photo will go and tell the kids not to write in the square.