Headteachers have been threatened with knives, subjected to gang attacks and had bones broken because of assaults from pupils and parents, Tes can reveal.
In one instance a head was "so badly kicked and bruised", it was difficult to see the colour of her skin afterwards.
Mark McCadeen, the headteacher of Birdham Primary School in West Sussex, said that at a conference of 140 headteachers from the county, he asked how many had been physically assaulted in the last year.
About three-quarters of the attendees raised their hand, he said.
Mr McCadeen, who said he had been on the receiving end of spitting, punches and kicks during his career, said violence inflicted on heads had a lasting psychological impact on the victim beyond the physical injury.
“It makes you sick to the pit of your stomach,” he said. “It makes you question why you bleed – literally sometimes – sweat and blood to do the job.”
He related four alarming cases which had been experienced by headteacher colleagues.
Two involved headteachers being threatened with a knife – in one instance wielded by a pupil, in the other by a parent. Both cases required the attendance of the police.
Another head sustained a life-changing injury after being kicked by a pupil.
A fourth head was "so badly kicked and bruised, you are hard-pressed to see the colour of her skin," he said. The assault was from “a group of pupils…a gang attack.”
In a further incident, a staff member at a previous school Mr McCadeen worked at was “threatened by a 9-year-old with a piece of jagged glass, waving it at her neck”. “She retreated to then be pelted by rocks and stones, with a tirade of verbal abuse,” he said.
Mr McCadeen's accounts were not the only cases of violence directed against teachers which Tes heard.
Carl Ward, chief executive of the City Learning Trust - which runs five schools in Stoke-on-Trent – and immediate past president of the Association of School and College Leaders, said a former colleague was punched in the jaw by a student in an unpremeditated attack.
“That teacher spent many years having a number of operations, having that broken jaw put right,” he told Tes.
Sarah*, a former cover supervisor, who worked at a challenging school on the south coast, was "shoulder-barged" by a pupil. In a later incident a "massive wooden doorstop" was thrown at her head. "The thing was about a foot long...with a very sharp triangular point and very heavy," she said.
Mr McCadeen said the situation facing teachers had got “palpably worse” in recent years, which he blamed on “a really worrying decline in children’s mental health" and the scaling back of support services because of funding cuts.
Paul Whiteman, general secretary of the NAHT headteachers' union, said: "Any kind of violence towards headteachers or their teachers or other pupils is completely unacceptable and can never be justified.
"These instances are still rare but they are significant for the individual involved and one incident is too many.
"These are people who are dedicating their lives to public service and education children. These are caring people who put children's best interests first. It's totally wrong that those honest endeavours - even infrequently - are met with violence."
Geoff Barton, general secretary of ASCL, said: "Schools continue to be very safe places generally speaking".
However, he said that school leaders were reporting to him that "behaviour has become a more significant issue".
Mr Barton attributed this to funding cuts reducing schools' capability to manage behaviour, the reduction of support services and a curriculum which did not engage some pupils.
*Not her real name
This is an edited article from today's edition of Tes. This week's Tes magazine is available in all good newsagents. To download the digital edition, Android users can click here and iOS users can click here