Teachers have always spent their own money on classroom materials. Some are cheap but many will spend 2 to 3K or more in a single year. How much they spend is not affected in the least by tax rules, in my experience.
Mrs. Homer spends about $750-1000/yr on school stuff. I just itemize it as cash charitible donations. (When I can get her to actually save the receipt.)
Teachers have always spent their own money on classroom materials...
Only the ones they personally used. Chalk, etc, was provided by school district. Pens and pencils and TEACHER notebooks were provided by teachers.