By Katherine Sellgren BBC News Online at the ATL conference

A female pupil phones her father on her mobile phone complaining that a teacher has pushed her off her chair.

A few minutes later and the father is in the school reception verbally abusing the women there.

They are so frightened, they call for the assistant head, Phil Baker.

I thought he was going to head-butt me - and he was bigger than me

Phil Baker

"We have a security door system, but unfortunately someone had flipped the switch and so this parent got into the building and I was left to face this irate man who was getting more and more aggressive," says Phil, who teaches at the Headlands School in Swindon.

"At one point I thought he was going to head-butt me - and he was bigger than me.

"In the office we have a panic alarm to the police and the girls in reception were so worried he was going to seriously assault me, they pushed it.

"Now the police faced him with protection, but I had nothing but my jacket and my pencil as a shield. I was totally shattered by the incident," says Phil.

'Parent power'

Phil says the troublemakers - a small minority of parents - had an attitude of mind which undermined teachers' authority.

"The biggest problem with parents like that is that they always believe their children - they never get the other side of the story."

Phil believes the problem of abusive parents stems back to the 1980s, when "a certain political party" coined the phrase "parent-power".

"They think they have the right to come in and do what they like.

"The sad thing is I could have been anybody and he'd have done the same - he'd already given the girls in the office a hell of a time.

"They just don't realise what they are doing to other human beings," Phil says.

Last laugh

The parent in this case was charged and brought before the courts, but Phil says the man still had the last laugh.

"His court appearance was in half-term, so I had to cancel a trip to Edinburgh.

"And then, the night before the trial, he changed his plea to guilty - so I could have gone away after all because I didn't have to give evidence."

And the pupil, it transpired, had not been tipped off her chair - she had fallen off.