Police were called in as furious parents staged a stand-off at a school after the last day of term was cancelled over prank fears.

The head teacher reportedly stayed in her office and refused to speak to parents during the three-and-a-half hour protest at Chatham Grammar School for Girls.

The row started after Year 11 pupils about to leave and start their study leave for their GCSE exams next week were sent home early yesterday and told not to return today.

The teenagers were looking forward to their last day in class so they could say goodbye to each other and their teachers.

However, about 20 minutes before the end of lessons yesterday, head teacher Christine Probin gave pupils a letter to take home to parents, telling them study leave started immediately and pupils would not be welcome in school today.

The letter said the decision was made after information was received from a number of sources that a small number of pupils were planning a series of stunts.

And because staff could not identify which pupils intended to start the pranks, the decision was made to stop all Year 11 pupils coming in.

The letter also apologised to pupils who were looking forward to planned assemblies and attending in fancy dress costumes.

But the move frustrated several parents who went along to the site in Chatham looking for answers and spent hours waiting to talk to the head teacher.

Eventually police were called. A spokesman confirmed there was a dispute involving parents and staff, but said no offences occurred.

One dad who went to speak to the head teacher was Martin Lane.

His daughter Rebekah was looking forward to her last day and was sent home early yesterday.

"If we as parents had just decided at the last minute not to send our child to school for their lessons, I would be fined for it, especially if I had no reason for it" - Martin Lane, parent

Mr Lane, 49, who lives in Gillingham said: "All four classes in Year 11 were sent home, that's about 100 students.

"The groundsmen and staff were standing at the entrances stopping them coming back on site.

"Myself and about eight other parents turned up and wanted to find out why this had happened at such short notice and asked to see Mrs Probin, but we were told she was in a meeting.

"I said I would be happy to wait until she had finished but I was met with a brick wall by staff.

"The groundsman were standing there with their arms crossed with other staff and I asked if I could knock on the head's door, but a staff member stopped me.

"He didn’t actually touch me, but kept moving around so I could not get near the door.

"Where is their duty of care for the pupils?

"If we as parents had just decided at the last minute not to send our child to school for their lessons, I would be fined for it, especially if I had no reason for it.

"We were there for about three and a half hours and were told the police were going to be called if we did not leave.

"When the police came they spoke to Mrs Probin in the office, so we know she was there.

"Eventually we did leave, but we had to leave without any answers."

Richard Elders, associate head teacher at the school in Rainham Road, said: "The decision was made on the grounds of health and safety for all our pupils and staff.

"Mrs Probin was not available yesterday or today and we had to act on the interests of safety."

Mr Elders also said the pupils' day would have been a short one and they would have completed their last lessons and left the site by 10.30am.

A spokesman for police said: "Kent Police was called at 4.14pm on Thursday, May 12, to a report of a dispute involving parents and staff at Chatham Grammar School for Girls.

"Officers attended to prevent a potential breach of the peace but no offences were reported."