TWO dozen schools are on alert after a girl was sexually assaulted and another helped fight off a tracksuit flasher that struck on a trip to their primary school toilets.

Police this afternoon confirmed detectives were investigating a sex offence involving two children, after an unknown man entered the Laburnum Primary School in Janet Street, Blackburn, about 11.30am yesterday.

Police said it was believed the man exposed himself to and sexually assaulted a girl, who was with another girl near classrooms on the school’s northern boundary.

The alleged attack occurred about 11.30am yesterday at the Laburnum Primary School in Blackburn.

Police said the man may have escaped from the school through parkland that borders the school.

Meantime, there are unconfirmed reports of a man behaving suspiciously at other schools in the Blackburn area in recent weeks, 3AW reported.

The radio station reported that the girls were walking together to a toilet block when they saw a man holding up his pants, which were undone.

He then grabbed the girl and when his pants fell down, he rubbed himself against her.

The girl’s friend then rushed to her aid and a “tug of war” ensued as the friend pulled the vicitm away from the man.

The girls broke free to alert their teachers.

Police continue to investigate, with detectives from Box Hill’s Sexual Offences and Child Abuse Investigation Team speaking with victims.

Team detective Acting Sgt Rosemary Eden said the Department of Education had been notified and police would be speaking to people in the area.

“A lot of people are aware in the area and the investigation is ongoing.”

The man police want to speak to about the incident is described as of Asian appearance, aged in his 20s, with an average build.

He had black hair which is longer on the top and shaved on the sides.

He was wearing a dark long sleeve top, dark trousers, and white runners with Adidas stripes. Sgt Eden described his hair as in an “undercut” style.

In the wake of the attack the school has instituted a safety crackdown, with extra teachers on yard duty and students being banned from walking between classes alone.

Education Department spokesman Alex Munro said the department was supporting the school in relation to the “very serious incident”, with 24 nearby schools contacted yesterday to alert them.

“The school has introduced a number of interim measures to increase student safety, including putting extra teachers on yard duty,” he said.

“Any students moving between classes outside are being accompanied by an adult or are in groups of four or more.”

The school provided an update to the local community yesterday, in line with guidance from police.

The school told parents the incident involved an “unwanted adult” near Year 4 portable classrooms next to a reserve.

Its alert to parents said police and the Education Department’s emergency management services were contacted immediately and interim procedures were put in place.

Principal Steve Richardson said the school was working with police.

“The safety of students is always our top priority,” he said.

“Yesterday morning two students were approached by an unknown man on school grounds, who exposed himself to them.

“The girls quickly brought the incident to the attention of school staff, who immediately contacted the police.

“We are taking this very seriously and have introduced a number of interim safety measures to further protect our students.”