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Besides the classical feature of student/teacher authentifications, the main particularity of virtual classes under WIMS is that the work and progress of students can be evaluated via real-time scores in a highly reliable way, based on \link{exercises}{exercises with random variations}. \link{1001/experience}{Our large-scale experiences} show that the system is able to check every student cheating attempt, except the fact that the server cannot verify the physical presence of the (true) student before his/her screen.