I also noticed you are going to be using PI Server for 50 RPI per classroom with a gigabit switch. Just curious how much power your system is pulling.
Do you have people inline that understand the system to operate it during use ? If something goes wrong, will they have resources to resolve it ? I've thought about using the PI Server but getting the training down from the start is tough in making sure they know what to do.
The class that I setup is running a small Linksys router, 22 RPI 3B+ desktops with older Dell 19" monitors with brightness and contrast at 50% or less and 2 RPI servers running at 450 ish watts on my inverter. I have thought about the PI Server, but having a few folks there being a little computer savvy to run and teach the class as it sits works well, but I've been hesitant to install everything on an x86 NUC.
My server is an RPI 3B+ running RACHEL with about 22 modules loaded onto a 120 GB SSD via USB. Each desktop has a 32GB MicroSD.
I use a 1 to 2 USB duplicator to make new copies of the Micro and SSDs and with them being cheap, I have spares onsite just in case.