the problem with old equipment twofold; first, there's a lot more maintenance. Next? when you are dealing in cast-offs, you by necessity have a heterogeneous fleet of hardware.

(The market for obsolete server hardware is interesting because often you pay more if you want a whole bunch of the same thing)

If you have to pay someone to maintain the obsolete hardware, it's probably cheaper to just buy everyone new chromebooks or something.

On the other hand, If you can sell that as part of the program, teaching the kids to fix the hardware, that could work out really well. But the point is that there is a lot of labor involved in using a heterogeneous fleet of cast-off hardware; a lot more labor than in using a homogenous fleet of newer hardware.

It is, however, labor that I think you can teach kids how to do. Fixing a computer isn't any harder than fixing a car, and is probably a lot safer.