Both my kids are in school.
For EVERY teacher they have had, they were given, (via a group gift from the class), a Camera. Gotten from Costco. Those sure shot types.
The Teachers, have ALWAYS.... really loved it. And almost cried.
Because, they don't have an in class camera to use, for their class and per projects/field trips/special occasions etc.
Another thing that the Teachers have ALWAYS loved to get, is an oscillating tower fan. Those don't take up much room, but it is needed in a classroom.
Those are the 2 gifts, that all of my kids' Teachers, have LOVED.
That and a group photo, of their class. Or a bunch of photos. And then put in a cute homemade album.
But the KEY thing also: is to HAND write, a card, for the Teacher. Telling her how much you/the family/your child, has appreciated everything she has done. Not a generic "thanks" card. But a heartfelt written card.
In my son's class, his Teacher was given a bookshelf. Made by one of the student's Dad. She badly needed a bookshelf.
As you know, many Teachers use their own money, to buy things for their kids and classroom. Things like cameras, fans, and bookshelves, are often not on their budget. And it is very appreciated and will be used for many years. And it is more than just a dust-collector or another of many mugs that they get.