Here's my honest recommendation, as a long time (arch) linux user.

Install windows on them.

As much as we see Linux as 'superior' here, and while that may be true in many ways - exposing them to something strange and different to any other pc they may encounter is probably doing them a disservice and will heavily impact the ability of the next 'techy person' to help support/fix anything down the line, since 90% chance that the next person in that role won't be a *nix admin, they will be some random who knows how to google answers and follow basic windows debug steps (nothing bad about that, but they won't be able to really fix anything themselves).

On the other hand, almost anyone can bumble-fuck there way through windows, everything has a gui and there is an ultimately more polished user experience - the wifi doesn't randomly break or hibernate doesn't take a day to set up etc.

Things are more likely to 'just work' the way people expect them to.

but my connection to get windows to put on it fell through while I was back home for a visit

If this is a financial issue i'll just throw out that outside of north america/Europe/oceania, I have never seen a home, school or even small business pc with legit windows.

A little bird tells me that 'the eye' has some install iso's and that if you search for 'kmspico' and 'windows toolkit' you may find some solutions to that problem.

On the other hand, if you are going to go down the linux path, install arch onto a computer that you use regularly and use it for atleast 2 weeks as your only OS, this will teach you how everything fits together, basic debugging, what to expect and generally how to function in the linux ecosystem.

Then install debian stable on the machines.

Write the root password in a sealed envelope, give it to someone trustworthy such as whomever serves as the school principle and ask them to pass it on to the next guy who comes to help out and asks for it - any extra documentation that you can scrap together should also be in there.