If I were in your position I would purchase the following scroll saws for the classroom:
Foot switch and magnifier with light. I might get some foot switches with Deadman switches and some with on/off switches for comparisons. Same for the magnifier lights, a 3X, a 5X, and a 10X , so the students will be able to compare.
A 22"Hegner
A 21" Pegas
A 22" Bauer
If you haven't exhausted your budget at this point, then I'd finish out with 14" single speed Hegner's.
Some of this would depend on if you have a break between classes ( on the order of a couple of weeks, for maintenance ). And if you have a skilled maintenance person.
The Hegner's only need oiling every 10 hrs of runtime, the Pegas and Bauer need the bearings lubed ever so often.
The Hegner's have been around for 50 years and have a proven track record. While the Pegas hasn't been around as long their are still a solid company. The Bauer saw is brand new, but it looks like the Pegas parts are interchangeable.
An example of why to have a 10X magnifier: