I wonder if Solus is the best choice in this scenario. Solus is a roling release distro with weekly updates. Even in case you get it set up: If you then want to install additional programs let's say 3 month later, you would need to run an update first. This might be several GB of size. How would you do that without internet connection?
And even after you install Solus, the first thing you need to do is to update, before you can install packages.
You might be better served with Debian for the school computer.
Best thing you do some research or ask AI what's the best way to tackle this problem.
Without any internet connection, things get tricky.
I mean, in theory it is possible to place downloaded packages in a specific folder that eopkg checks. But eopkg wouldn't even now what version of the packages is the latest, since it can't update it's database without internet connection.
I don't see a way how this could be easily achieved. Maybe others have some ideas here.
Edit: if the computer has a wifi card, or you have a wifi USB adapter(if you get it to work without prior internet connection in case the dongle would need drivers) you could use let's say a smartphone as mobile hotspot for internet connection. But then you need a mobile plan with many GB.