Article: From the 1950s on, the students were also used for unpaid work at schools, where they cleaned and performed repairs. This practice has continued in the Russian Federation, where up to 21 days of the summer holidays is sometimes set aside for school works. By law, this is only allowed as part of specialized occupational training and with the students' and parents' permission, but those provisions are widely ignored. In 2012 there was an accident near city of Nalchik where a car killed several pupils cleaning up a highway shoulder during their "holiday work" as well as their teacher who was supervising them.

Now answer this question: When were students used as workers?
1950s