Statistics obtained by the Yorkshire Evening Post show that in the last two years there have been 159 serious physical or verbal assaults on the city's school staff.

Today, leaders at the teachers' union the NUT said while those figures were alarming enough, scores more attacks were going unreported because heads didn't want their schools to get a bad name.

NUT health and safety adviser and Leeds teacher Tim Hales told the YEP: "The worst case I have dealt with was a teacher who was set upon and hurt quite badly. He was attacked while at his desk so was completely unable to defend himself.

"The level of assaults is worrying, especially as we know that there is such a high level of under-reporting of these incidents.

"A lot of heads are not encouraging their staff to send in reports of assaults because they don't want the school to get a bad reputation.

"The response from some managers seems to be that it is an occupational hazard. That is a very sorry situation."

Education Leeds, which runs city schools, says it takes school violence very seriously and supports schools to deal with such incidents.

The figures were obtained by the YEP under the Freedom of Information Act.

They show that between April 2007 and March this year, police had to be called into schools 183 times.

Of those, 24 were assaults by pupils on fellow students, but 159 were attacks on school staff.

Many were at special inclusive learning centres (SILCs) - former special schools – or pupil referral units (PRUs) where youngsters have special needs or have a history of problematic behaviour.

However, a significant number of assaults also took place at mainstream secondary and even primary schools.

The worst offending school was the Elmete Central SILC at Stonegate Road in Meanwood, followed by the Burley Park Centre PRU which had 18 physical assaults and two verbal ones.

The worst mainstream secondary school was South Leeds High in Beeston which had 18 physical attacks and one verbal assault.

Beechwood in Seacroft was the primary with the worst record, having to call in police to deal with four physical assaults and one verbal.

Mr Hales has now called for class sizes in some schools to be reduced and for more specialist training for staff in diffusing potentially violent situations.

He said: "In certain inner-city schools where kids come from quite difficult backgrounds and where there has been poverty and other problems, there should be smaller class sizes.

"There also needs to be more training in de-escalation techniques so that if a teacher is confronted they have the techniques to deal with it."

Chris Edwards, chief executive of Education Leeds, said: "Safety within schools is of paramount importance. Education Leeds and schools are working hard to educate young people about their responsibilities towards each other and the wider school community.

"Our Safer Schools programme has helped reduce incidents of unacceptable behaviour and increased the understanding of the need for respect and tolerance.

"The majority of the 183 incidents occurred in either our PRUs or the SILCs that cater for young people with complex behavioural needs.

"We are committed to providing support to all our schools so young people across Leeds continue to be happy, healthy, safe and successful.

"When an incident occurs, our schools act quickly to take the necessary steps to address it – with the full support of Education Leeds."