If she brings her lunch like I do consider a quality backpack cooler bag. It’s basically a giant lunchbox with room for other stuff and totally hands free (teachers tend to overcarry crap back and forth). The one I liked most isn’t made anymore but I’ve found a few on Amazon that I’ve given as gifts just not sure of longevity yet.

Another favorite of mine is a massive metal water bottle. Obviously yeti and swell and the like make some good ones. I think customized with her name is how you make it personal and it also saves a teacher who can easily leave it on accident at places like a staff meeting. Hydration is important.

Finally you can’t buy it for life but a year subscription to a local place to get a once a month massage would be a high end superior teacher and wife gift!