Australian Associated Press

Students at a Melbourne boys' school have been evacuated to an oval because a man entered the school grounds acting aggressively.

The man walked on to the school grounds at Melbourne High School in South Yarra about 2pm on Friday and staff called police.

"There was an unknown man on the school grounds being a little strange," a police spokesman said.

"Some of the students were evacuated onto the oval as a precaution."

Police arrested the man, who is in his 30s and unarmed, and he was taken to hospital for assessment.