71 years ago, they introduced tuition fee in senior school and institutes of higher education of the Soviet Union.
In schools of Moscow, it was 7$ a year and 5$ for small-town schools. As for higher education, it was 13$ for Moscow and Leningrad, and 10$ for other cities. Yearly tuition payment could be compared with an average monthly wage of a Soviet worker. However, for many Soviet people, introduction of tuition fee ruled out the possibility to continue education after the 7th grade (for example, people working at collective farms at that time did not receive salary at all).
As a result, number of high school graduated reduced by two and it was exactly what government wanted. The point was that the country needed work force to work a machine.
Moreover, in the 40s, government adopted a law according to which young people over 14 could be called up to study at technical secondary schools to later work at factories for at least 4 years. Violation of the law and misbehavior resulting in expelling from school were made penal.
In the picture: carpenter pupils.
The only social ladder for the lower class became military schools where education remained free, or working in the People's Commissariat for Internal Affairs after active duty.