I get what you're saying, OP!
I've done the gift cards, but, if you're looking for something other than gift cards, I've also done the following:
* A jug drink dispenser w/ some lemonade mix, a package of springy/summery napkins & matching disposable cups, a plastic picnic tablecloth, & some fun straws w/ a little tag that said, "Thank you for a great year! We hope your summer is a picnic!"
(I've also done something similar to the above but, instead of the jug drink dispenser, I used one of those collapsible picnic baskets.)
* A divided chip platter (I found some really nice pottery ones on sale) w/ a bag of tortilla chips & a jar of salsa w/ a little tag that said, "Here's to a summer full of siestas & fiestas!"
* A beach towel w/ a gift card to a local bookstore - "Here's to Lazy Days & Beach Reads!"
* A bird feeder w/ a little tag that said, "Wishing you a 'Tweet' Little Summer!"
Currently, we homeschool, but we are members of a weekly co-op, & our kids usually have a combined total of about 9 teachers. One year I gave each a hummingbird feeder. Last year, I gave each a reusable water bottle w/ an individual packet of lemonade. This year, I gave each a succulent.
I've been a teacher & know teachers get lots candles & mugs & #1 teacher figurines, so I always try to stay away from that kind of thing. Gift cards (no matter the amount) are always welcome! However, I also know that most teachers are very appreciative of whatever they receive and most especially love the handwritten notes!