Yep, that is why my family moved to the US from Russia. My mom wanted to be a doctor, but wasn't accepted to medical school even though she got straight As and was completely qualified. They just said they can't accept her because she's Jewish, and there is nothing she could do about it. I'm really glad I got to grow up here in America.
Perelman came up in the Soviet system in the 1980s, when the discriminatory practice you mention was in force:
http://www.nybooks.com/articles/archives/2010/apr/29/he-conq...
Relevant quote:
"For a Jewish boy [sic] gifted in mathematics to be admitted to a university, there were three possibilities: hope you were one of the two Jews accepted at Leningrad University every year; go somewhere with less draconian admission policies; or make it onto the Soviet team for the International Mathematical Olympiad, which guaranteed admission to Leningrad University. Perelman decided to try out for the team."