I would recommend Debian, I use it so I am use to it and would love to see it in Australian Education, but I would recommend to you that you consider
Red Hat Enterprise Linux as well. To me the difference would be if you use Debian you have the Debian (and wider Linux) community to help you but if you use Red Hat you pay a subscription fee and Red Hat themselves help you. To me it all boils down to your level of confidence in your own ability.