Gift certificates are great.. my best friend is a teacher and i am studying to be an elementary teacher and with the lack of money out there for teachers gift certificates do wonders...
my best friend actually REQUESTED that i not give her a birthday present (we usually make each other something) and to give her a gift certificate to either Target or Walmart.
I ended up getting her one to Walmart which sometimes has better deals. With that she can pick up extra pencils and folders and any misc supplies like tissues and hand sanitizer.
For the teachers I am working with for my field internship (part of my program) i got them cute mugs and stuck a candy cane and a gift certificate. then i wrapped it in celophane with some pretty holly leaves and berries stuck into the mugs and pretty ribbon on the outside.. they looked expensive and cute but they were all homemade