In Osogbo, 35 students from Fakunle Comprehensive School were taken to the hospital after inhaling teargas fired by riot police.
Some students became unconscious.
Parents rushed to the school to check on their children. Some parents took their children home while others were directed to hospitals where their children were being treated.
The Permanent Secretary of the Osun State Ministry of Education said the situation was being handled.
When contacted, the spokesperson for the Osun State Police Command, Yemisi Opalola, said the riot policemen were engaging in their usual morning drills and apologised to those that were affected.