Nearly a third had encountered verbal abuse in the past 12 months, with a further 17.5 per cent the victims of violence, according to a study by Unison, the main union for school support staff.

The high levels of risk that teaching assistants are exposed to have come to light as the union campaigns for a higher pay rise than the 0.5 per cent currently on offer from local councils.

Christine McAnea, Unison’s head of education, said it was “shameful” that teaching assistants should be expected to put themselves in danger of being attacked or abused.

“Many of our members work with children with special educational needs, often with challenging behaviour,” she said.

“It is time the hard work, long hours and commitment that teaching assistants put into their jobs was recognised with higher pay.

“It is a disgrace that they have been offered just a 0.5 per cent increase. This will go nowhere near to helping them cope with the recession in the tough year to come.”

Unison’s survey questioned 535 teaching assistants in schools across the UK. Slightly more than 7 per cent of those who responded said they had experienced violence so serious that they had required medical attention.

Fourteen per cent said they knew a colleague who had needed medical attention following an assault.

These figures mean that of all the local government employees surveyed by Unison, only staff working in social services were more likely to be assaulted at work. Social services staff were also the most likely to suffer direct verbal abuse, with 65 per cent reporting an incident in the past year.

In total, there were 18,590 suspensions and 980 exclusions for pupils who had been violent against adults in primary, state and special schools in 2006-07, the latest year for which figures are available.

Ms McAnea called for schools to have clear policies and procedures to deal with violence and abuse. “There should also be more comprehensive risk assessments to anticipate dangerous and difficult situations,” she said.

Unison and the other local government unions are due to meet employers on Monday to discuss their claims for a bigger pay rise than 0.5 per cent. Teachers will receive an increase of 2.3 per cent from September.