Just to clarify, this behavior is only happening on the school network? Does it happen only to instructor computors on the school network?
Just to verify is LabVIEW being run as an administrator (right click, run as administrator) on the non working computers?
Can you try mass recompiling the LabVIEW class folder? You will need to point to the folder with the Brickreference.lvclass. Mine is here: C:\Program Files (x86)\National Instruments\LabVIEW 2015\vi.lib\NXT\LegoClasses\BrickReference