I agree - I couldn't recommend eBay for buying a printer - caveat emptor. However, if you can get a refurb II or III series from a company that will give a warranty, they are great, reliable lasers. A 4000 series is probably overkill for a school,
The HP 4000s are very good indeed, in terms of speed, networkability and reliability, but if it's for low-volume reports, then a shared Deskjet could do nicely - and you'd have the plus of colour as an option.
As an example; The HP 5550 is a great printer, if you've got USB 2.0 to take full advantage of it. It can do 17ppm, gives an estimated 3,000 pages per month and has a 100-sheet capacity paper tray.
Maybe consider an all-in-one such as an OfficeJet to give the options of scanning, colour photocopying and faxing at half the price of the LJ4000s. Note that Scanning can only be done locally, and reliability of these things can vary wildly.
Only problem with Inkjets is reliability at high volumes, and frequent replenishment of consumables (low volume paper handling and ink cartridge replacement). Low volume, they're great and last for years. Some staff at one of my sites are still using DJ500s shared between 5 - 10 users. But their budget is very low.
Bottom line - project your printing volume needs and check out the costs of the associated consumables (toner, cartridges) and their lifetime. This should give you a better picture of the actual running cost of the printer.
Hope this helps CitrixEngineer@yahoo.co.uk