A school has issued a warning to parents after pupils were threatened with a knife in one of a spate of muggings.

Highgate School, in North Road, says it is increasing the number of staff surveying the area after school hours to keep children safe.

It comes after a several pupils in the senior school reported incidents.

Deputy head Rebecca Golland emailed parents to say “a number” of pupils had been approached on their way home from school by a group of four males – believed to be 16 or 17.

During these encounters, the teens are alleged to have mugged or attempted to steal items from students.

In the email, the deputy head told parents: “In one incident, this involved our pupils being threatened with a knife.

“We believe that this is the same group involved in all of these incidents and have alerted our community police officers and security staff.”

It is understood that in at least one incident, students were walking in Southwood Lane on their way to Highgate station.

Parents were assured that such incidents “remain relatively rare” in the borough.

In an update issued this morning (June 23), the school confirmed there were more attempted muggings yesterday (Thursday).

The email read: “I wanted to first commend all the pupils who emailed staff immediately or who returned to school to alert a member of staff, this was incredibly helpful in ensuring that we were able to contact police quickly and keep pupils safe.”

To tackle these repeated incidents, staff will be patrolling the area and “additional security staff” will be present around the Southwood Lane area.

Police have advised pupils to walk in pairs, cross the road if suspicious about a group, and to approach a house, shop or return to school if in danger.

A Highgate school spokesperson said: “We have passed police advice on to our pupils and parents and we will continue to work proactively with local police to ensure that pupils are as safe as possible on their way to and from school.”

The Metropolitan Police have been contacted for more information.