For the teachers I like to get together a box of school supplies... crayons, pencils, etc. This time of year things start to get worn out so new is always appreciated.
I bought a BUNCH of Bath and Body Works soaps on clearance. We are sending those with my middle school child for her teachers (7) and putting notes on them that say 'We wish you a germ free Christmas, we wish you a germ free Christmas, we wish you a germ free Christmas, and a soapy New Year'
My son's teacher we will buy a more personal gift for. I work at his school so his teacher is my co-worker as well as my friend and his teacher. She's pretty special.
For classmates we do small goody bags with little trinkets. We buy a gift for the classroom every year. A game, a Lego set, or something. I usually ask the teacher for recommendations. This year I bought a couple of $5 games from the Black Friday pre-sale. I will give them those and something my son decides upon.
My daughter (12) gives gifts to her friends. I found a good deal on Caboodles acrylic nail polish trays so she is giving them those and making them sashay scarves.