The students were conforming. As this paper [1] explains, people -- especially young people -- will often answer incorrectly in order to gain social acceptance:

"...the group answered incorrectly on purpose; it appears that when we are unsure of how to perform a task or how to behave, we may take comfort in agreeing with a large number of other people."

[1] http://www.personalityresearch.org/papers/lumbert.removed