School staff saw red after midnight vandals went on a pink paint spree and redecorated a mobile classroom.

Teachers arriving for school were stunned to see the once dull prefab was suddenly a new, vibrant shade of shocking pink.

Police were alerted and inquiries are under way to trace the culprits who struck in the dead of night.

John Foster, head of Ponteland Community High School, in Northumberland, has appealed for anyone who knows who carried out the shocking pink attack to come clean.

"This isn't a joke or a prank," he said. "This is criminal damage and it'll cost hundreds of pounds to have the unit professionally re-painted.

"It was discovered early on Monday by staff. Whoever did it must have taken some considerable time, depending on how many were involved.

"They used rollers to paint the walls and frame."

An end-of-term get together for sixth-form school leavers and staff last Friday was expected to produce high-jinx from the pupils, but Mr Foster said there were no problems and everyone left quietly.

"The premises were secure and we believe the damage was done sometime between Sunday night and Monday morning when the caretaker discovered it."

The unit, which holds 25 to 30 pupils, is at the rear of the school grounds in a more secluded spot.

Police believe the phantom painters crossed the school fields to get to the classroom under cover of darkness.

There were no signs of a break-in which would have triggered alarms, and nothing was stolen.

Last week police stepped up patrols in the area at weekends after complaints about rowdy gangs of youths travelling to the area to cause disorder.

Six arrests were made the weekend before in Ponteland for alcohol-related offences, including drink-driving, being drunk and disorderly and breach of the peace.

A large quantity of alcohol was seized and disposed of after a gang of troublemakers ran off when police arrived in the Broadway area of upmarket Darras Hall.

Police say some of the youths involved are being driven to Ponteland from Newcastle by their parents and dropped off on Friday and Saturday nights.

Northumbria Police Insp Mick Connelly, who covers Ponteland, said: "We have responded to reports of problems caused by youths gathering here at weekends in particular.

"However, at this stage there is no evidence to suggest the school classroom was targeted by a gang of outsiders. We're looking at what appears to be two separate issues."