Montreal police declared the march illegal under bylaw P-6 and blocked the roads leading away from Parc Émilie-Gamelin.
Students marched through the park and right into traffic on de Maisonneuve Boulevard instead.
They were comparatively few in numbers, and police quickly moved in to kettle them.
Between 150 and 200 people were arrested for participating in an illegal demonstration and were loaded into nearby STM buses.
Police said almost all of them will be given a fine and released.