In a letter sent to parents on Tuesday afternoon, school principal Anne Coutts said she had received several reports of disturbing incidents in the Red Hill area during the past few days.

"On separate occasions children have been asked to enter the car and to hand over their school bags," she said.

"Fortunately all children involved in the incidents managed to get away but clearly the matter is distressing."

Ms Coutts said police were investigating the matter and Red Hill Primary School and Canberra Boys Grammar were also aware of the incidents.

"We encourage children and families to be extra vigilant in the area in the coming days – as we will be – and would ask you to take this opportunity to remind all children of stranger danger," she said.

"Please reinforce to your children that they should never enter a stranger's car under any circumstances, and that younger children in particular should avoid walking alone."

Ms Coutts said teachers would be on duty from 8am at the junior school and asked parents not to drop their children at the school before this time, unless for music rehearsal where supervision was provided.

"Junior school students being picked up after co-curricular activities should be collected immediately after the session directly from the supervising staff member or coach at the designated area," she said.

"There should be no other pick-up arrangements or locations."

Ms Coutts urged parents not to meet their children in surrounding streets and to report any suspicious behaviour to police on 131 444.