The lockdown at Central Peel Secondary School in Brampton has been lifted.
The school was under lockdown because Peel police were investigating a robbery near the school on Kennedy Road South.
Three people are in police custody.
Police responded to a robbery call near the school on Kennedy Road North over the noon hour.
Madoc Drive Public School which is nearby was under a hold-and-secure order as a precaution, but that was lifted as well.