Ok, our solution is not so minimal, but it is modular, so you may disable/remove parts of the system you would not need.
Check, check, check.
Not an ISO, but we boot and install from scratch the clients using PXE booting. Your installation is limited by media on which you may have the ISO: we are using the LAN for the lab and installing 25+ clients all at once.
Yep, we do that 
except we are doing it from scratch instead of having already a backup configuration to restore.[quote=“yakman000, post:81, topic:2132”]
This could be a “Nethserver starter kit” to the schools…
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That’s what we are trying to make with our project. Again, for the sake of completeness, you may find here all the stuff needed in GNU GPL v3.0.