Teaching unions say the situation at Fernhurst high, Blackburn, a school for pupils with emotional and behavioural difficulties (EBD), is out of control.
But the local authority says that behaviour is no worse than that at other EBD schools. The TES understands six Fernhurst teachers have needed medical treatment after incidents at the school this academic year.
Unions have recorded a list of serious incidents over the same period, including 10 involving personal injury. They include a teacher being butted in the stomach, a member of staff losing feeling in their legs after an attack by a pupil and a chair being thrown at a member of staff who was then punched in the face.
Lancashire police said they had recorded 12 crimes at the school between September and October last year, seven of which were assaults and five were incidents of criminal damage.
Lesley Ham, local NASUWT secretary, was quoted in the Lancashire Evening Telegraph as saying: "These incidents are just the tip of the iceberg. Most of the incidents don't even get reported and I have bags of evidence of teachers' reports of other serious incidents."
But Peter Morgan, Blackburn with Darwen Council's interim director of children's services, said: "From experience, the accident forms relating to Fernhurst, which included incidents between pupils and a pupil accident, are in line with other similar emotional and behavioural difficulty schools nationally which are dealing with the most challenging young people."