I think parent is right, no international students likely means higher tuition for everyone else. If you're in doubt, ask someone who works in admissions, I expect they'll tell you the same thing.
http://blogs.wgbh.org/on-campus/2014/6/17/international-enro...
I think this is even worsened by the fact that foreign students pay directly towards the university and become a primary source of revenue and the 'regular' students money is tertiary (state) or secondary (scholarship) which has conditions and delays attached.
I guess it is probably the same all over the world.
It is higher, but for out-of-state and international students. That's how public universities have been able to offset low in-state tuition and raise more financial aid.