I have sold various Manufacturers over the last 35 years and I swear by the Toshiba devices. They are robust and reliable. This is clearly also down to the service support. Develop are branded Konicas and generally have a good build quality. Kyoceras are good as Mono only devices, they haven't managed to get the colour system right yet. I would also say that Canon, Sharp and Ricoh are also fairly good. I wouldn't touch any other brands for Education use if you want quality and reliability.
Regards.
Alan