When I was teaching I told my students that if they really felt they needed to get something for me it either had to be hand made (can't get enough of those paste covered creations) or they could buy a book for the school library in my honor. All these years later, I have the heart-felt crafty stuff all over the house, and the school library still has great books.
You could have the kids make a mini-fleece wrap for the teacher to throw over her shoulders--I was always chilly after school--the heat went off as soon as the busses pulled out but I stayed to finish my work there instead of at home.