The threats have led to a police presence at St Bartholemew's primary school in Swanley, Kent, where clergy, parents, governors and children have been involved in months of argument and protests.
Leaflets have been handed out at Mass, petitions have circulated and pupils have been disciplined for chanting in the dining hall. The former head, a nun, is taking her case to an industrial tribunal while the governors, chaired by the parish priest, have threatened legal "restraint" if she tries to return.
The case has even reached the Secretary of State for Education and the Archbishop of Southwark.
The row is over the future of Sister Clotilde, 56, a member of the Sisters of Mercy order who ran the school for 13 years until last summer. In that time St Bartholomew's had seemed a happy school and was one of the most popular in the area.
But three days after Sister Clotilde left on holiday in July, governors decided that in future she must ask permission before buying books or equipment or ordering any work to be done.
They wanted to divert cash to pay for a pounds 40,000 playground which was originally to have been funded by the parish. The parish priest, Father Seamus Hetherton, said churchgoers were unhappy about the amount of money which the parish had given the school in the past.
Sister Clotilde, responsible for the day-to-day running of the school, returned to find she could no longer take even the smallest financial decision. She wrote a letter of resignation, but retracted it two days later.
The governors, however, had already heard Father Hetherton say he could no longer work with Sister Clotilde and they must either accept her resignation or his. They chose to accept hers, and two governors came to the convent to tell Sister Clotilde she should not return to serve her notice. The next day, as the autumn term began, parents were told she had left for personal reasons.
"It's the sort of thing you expect in some business in the City but not in a place like this. It seemed so brutal,"said Aidan Coen, a parent who has supported Sister Clotilde.
As the case divided parents, bitterness became entrenched at the school. Within days of Sister Clotilde's departure, previously loyal staff apparently signed a letter saying they would not work with her if she returned. A parents' letter of support for her was signed by 118 people, but many more supported the governors' actions.
Both camps complain of verbal abuse at the school gate and on one occasion a police presence was requested as parents handed out leaflets.
Children have complained of bullying in the playground as a result of the dispute. Some of the school's 300 pupils were disciplined for chanting "We want Sister back!" in the dining hall.
When rumour spread that Sister Clotilde was coming back to reclaim her position, two governors delivered a letter to her that if she did so they would take action, on their solicitor's advice, to "restrain" her.
While some parents are now thinking of removing their children, others simply want the school to return to normal. Few had reported any problems before the summer, but some say they prefer the new management under an acting head teacher, Sarah Jennings.
Lorraine Whitmore, whose son and daughter attend St Bartholemew's, said: "Since September the school has been run very well. The atmosphere is completely different. The kids are much more confident now."
Although the trustees, who include the Archbishop of Southwark, have appointed one of the protesters, Leslie Fernandez, as a governor, the controversy has spilled over into the parish. Governors' supporters leafleted worshippers at Mass asking them to phone local newspapers in support of their parish priest.
For her part, Sister Clotilde appealed to Gillian Shephard, the Education Secretary, but although she accepted that governors should have given the head notice of their July meeting, Mrs Shephard refused to intervene. The former head, who has remained in the convent throughout, is now taking her case to an industrial tribunal.
The threats came two weeks ago. Parent protesters received anonymous phone calls saying a group of men had been heard planning a "hit" against three of them in an Irish club. One of them was a "psycho", the caller said, and he himself was afraid of "having his kneecaps done". If they were planning to take their children to school on the following Monday - last week - they should be careful.
Another caller simply hissed: "Watch your step!"
The mother who took the calls, who does not want to be named, doubts that the threats would be carried out but is still terrified. She plans to remove her children from the school and has asked the council for a house in another area.
"My children couldn't understand why they didn't go to school on Monday. I am just really depressed," she said. The police have kept an eye on the school, though they do not believe any crime has been committed.
Father Hetherton, meanwhile, has also reported receiving calls from someone threatening to burn down the presbytery at his Church of the Holy Apostle. He was away last week and the vice chairman of the governors Mr John Horner declined to discuss the matter. "It is in the hands of our lawyers and we are advised to say nothing at all," he said.Reuse content