A school has banned parents from entering without an appointment after staff were subjected to verbal abuse.
Ebbsfleet Academy, in Kent, said the measure came after a minority had been "violent and abusive".
One mother's four-letter outburst - in which she can be heard shouting and swearing - was recorded in the school's reception area.
Principal Alison Colwell said some parents had been banned for the safety and wellbeing of students.
Some of the behaviour was the worst she had seen in her 25-year career, she said.
"The students don't deserve to witness that, to hear that. My staff don't deserve to be subject to that. All of the people that work here are totally committed.
"As part of your working life to have to take that level of abuse is just unacceptable."
The school said threats of violence had also been made, but did not reveal further details.
Ms Colwell said all staff could be contacted directly by email and she was always prepared to meet any parent with an appointment to discuss their child's education.
She added: "The problem is with a small number - parents coming in angry, aggressive, demanding to see a member of staff at a certain time, which clearly isn't practical or workable or what would happen in any other organisation."
Julie Huckstep, from the Association of Teachers and Lecturers, said: "It's the first instance that I've heard of, certainly in this area, of violence from parents towards staff.
"But yes, teachers need to be protected. If you go to any public building, there are signs saying 'we won't tolerate violence' and why should schools be any different?"