T.F.
Up until the 5th grade when my daughter had 1-3 teachers, I gave gift cards that would cover a movie for 2 and a snack at Cinemark (usually $20-25)
Since she started 6th grade and is now in 7th, she has 7-8 teachers so I get giftcards from Starbucks with anywhere from $10-$15 on them.
Other gift card options are for Barnes and Noble, Spa certificates for manicures/pedicures, etc.
They all seem to like these.
Susan