A woman has been charged over the alleged sexual abuse of a student while she worked as a high school teacher on Sydney's northern beaches.

Police arrested the 50-year-old at a unit in Dee Why this morning.

They allege she groomed a 15-year-old boy for sex and committed sex offences while he was under her care at a Sydney school in 2008.

Police say some of the incidents took place in a classroom.

The woman is to be charged with five counts of aggravated sexual assault and two counts of an aggravated act of indecency.

She worked at the school for three years from 2005.

Police are investigating whether similar offences took place at other schools where the woman taught in Sydney's north.

Detective Inspector Luke Arthur says investigators want to speak with anyone who has information.

"Back in the period from the mid-2000, say 2003 through to 2010. We're just calling anyone that may have had a relationship which is a bit different to the one that a normal student-teacher relationship may have just to come forward and speak to us," he said.

A spokeswoman for the Education Department says it cannot yet comment on the case.