We ask our child who she considers to be impactful or exceptional teacher(s) for the year. Our child goes in and personally thanks him or her at the end of the school year. She also delivers a note from us reiterating our appreciation with a gift card enclosed. Our child usually does the sleuthing to find out what may work best -- gift card from bakery near school, Starbucks, B&N, Target or Amazon etc. It is usually only a few teachers per year, so not a big deal. They have Teacher Appreciation Week in May, so we already have thanked them
once.

OP- we do not give any gift cards out during the school year. We do send them in at the end of the year.

A handwritten note from a student is greatly appreciated!

It is not the norm but I was always touched by either a note and greatly appreciated a Starbucks gift card.

No, but a nice note is fine. Remember that these are professionals who will be writing letters of recommendation for colleges. Think ethically and act accordingly.

My oldest son is a freshman at a private high school. It's his first year there and I am not sure what to expect.
Is it the norm for high schoolers to bring gifts to teachers? If so, what would be some good gift ideas?