Yes, it would be a good idea to rinse the tank, filter (if you end up getting one), heater, gravel, and decorations beforehand, to get rid of dust particles.
If you're getting a filter and will be doing the fishless cycle, then you will need to have the filter running in the tank without the fish for about a month.
If you opt to add the fish right away, then you will need to acclimate him to the water by floating his cup in the tank while gradually replacing the water in the cup with the water from the tank (about every 15 minutes). After that, all he needs is a heater set to about 78 F, 3-4 pre-soaked pellets per day, and clean water (i.e. frequent 100% water changes for an uncycled tank). You don't need to feed him at all over the weekends.
If your principal won't allow the filter to be plugged in overnight and you would rather not have to do frequent 100% water changes, then you may want to consider setting up an "el natural" style planted tank, using potted soil as a substrate and filling half of the tank with low-maintenance plants such as java ferns, Amazon Swords, Anubias, and hornwort. Here's a step-by-step guide for a planted tank that someone did for her office:
^ I think this would be more educational and the fish would have more fun with real plants.
I don't see a way around not having a heater plugged in overnight though. Insulating the tank overnight/weekends with a styrofoam box, newspapers and a heat pack might be an option but the heat packs would end up being costly.
By the way, here is a link for the cheapest water testing kit:
Oh, and one last thing - I think you should advise the cleaning staff to not touch the aquarium. Not to change the water, feed the fish, and especially not to clean the aquarium with Windex.
Good luck to you! Your students are lucky... I once had a fun and effective teacher who let us keep tadpoles in the classroom and it was a great experience for a kid who wasn't allowed any pets at home.
You are way too nice! Every single one of her posts on this thread confused the heck out of me. I had no idea her initial post was sarcastic either.