As a follow up question to OP's question, how common was it for Soviet universities to increase the difficulty of the entrance exams for, so-called, "undesirables"?

This article highlights the unfairness of entrance exams given to prospective Jewish students at the mathematics department of Moscow State University. Was this the norm?

The answer is going to be extremely dependent on period. University entrance in the Soviet Union in the 1920s versus the 1980s is going to be considerably different. Far more different than if you made the same comparison in the West. Is there a particular time frame that interests you?

Follow up did soviet citizens choose their studies or was it chosen for them.