School workers have been spat at by pupils, had objects thrown at them and even had car brakes cut and windscreens smashed, a teaching union conference has heard.
Staff are often reluctant to report violence, due to a belief that it is "part of the job" or a feeling that it is not worthwhile, the National Education Union (ATL) section was told.
Delegates at the union's annual conference in Liverpool have raised concerns about "the increasing lack of oversight of violent behaviour by students towards staff".
The Government said it has given schools powers to tackle poor behaviour, and that schools should have procedures in place to deal with these issues.
Peter Shreeve, a delegate from the Isle of Wight, said: "In my experience staff are often reluctant to report violence. Some believe it's part of the job and being assaulted is accepted and expected.
"Some think reporting is not worthwhile, as there are no consequences or management is reluctant to act."
He said there was evidence that violent assaults have gone up in the last five years, and that he was "personally aware" of objects being thrown, heavy objects being slammed into bodies and spitting as well as "car brakes being cut and a back windscreen being smashed on a member's home drive".
He told the conference: "A primary headteacher recently told me a member shouldn't return to work after their summer operation as the nature of their new pupil intake in a primary school had led to restraint training for all staff.
"And even though most of their time will be spent in an office, it would be extremely prudent if they didn't return for some time."
He said: "What we are calling for is educational glasnost, increased openness and transparency.
"We're calling for well-understood procedures where all staff report all violent incidents which are always recorded as safeguarding issues.
"We're calling for a system where all institutions report centrally but at a local level. We're calling for a reverse of austerity. Children now receive less support than they used to, staff have no time whatsoever to deal with issues, hence an increase in anxious students lashing out."
Corrie Rayner, who works as a science technician in a large academy on the Isle of Wight, said: "A few months ago, during breaktime, I encountered a large group of Key Stage 3 students in the corridor and when they reached me, one student intentionally pushed another student towards me and made me trip.
"Luckily, I was not delivering a tray of acid to the lab, which is not uncommon."
She said in another incident she was "mock headbutted", adding: "You may say that these are only minor examples of the kind of aggression and violence that has increasingly found its way into our schools."
The NEU passed a resolution which noted that "academies, free schools, etc have no legal responsibility to report incidences of violent behaviour and can hide their figures outside of the local authority, within their own organisation."
It called on the union's executive to encourage members to report acts of violence and investigate how violent behaviour is reported and collated, and by whom.