Chernetsky, who is from the Ukrainian city of Odessa, has heard concerned reactions from friends back home.
Mickey Cesar says his Ukrainian students are like his children.
The regional tensions filter down into everyday life in Kiev.
Sometimes, it's hard to picture a conflict that's happening thousands of miles away.
Although there are rumors that Russia will not stop with the Crimea, Cesar doesn't see that happening without a fight.
Last weekend, there was a vote in the Crimea over whether the region should become part of Russia. The United States and European Union have said was illegal under international law.
Although the election results seemed to be overwhelmingly in Russia's favor, it may not be so clear-cut.