Police provided few details of the incident, which happened shortly after 9am, but said it was ''resolved peacefully'' and without anyone arrested.
Elmgrove School principal Chris McKinlay confirmed classrooms were secured after a person carrying a knife was seen in the school grounds.
''All the children were in classes at the time, so they were well away from the incident and safe at all times,'' Mr McKinlay said.
Parents were notified of the incident yesterday afternoon.
''It was reasonably short and resolved quite quickly,'' he said.
He could not discuss specifics of the incident, he said.
A police spokeswoman said police were called about 9.10am.
No police action was required and police had no further involvement in the matter, she said.