Despite an impeccable record for more than a decade, she is so shaken by the experience the 46-year-old says: "I will never, ever go back into education."
Mary had been at the school for more than a year when the bullying by nine teachers began. "When I tell people what I was subjected to I get two reactions," she says. "Those who know me cry; those who don't, jaws drop."
Her head was sympathetic but helpless when a complaint was first made against her. "He said, 'These allegations are so trivial, you'll be fine. It will be done and dusted in a fortnight, but we need to investigate'."
Mary was accused of saying that a colleague had bad posture and over the next six months such "trivial" claims against her escalated rapidly until the consequences were felt in her personal life too.
Her mobile phone number was subscribed to a pornographic website, home address added to an online gambling site, and within a few weeks of changing her telephone number, men were calling her from phone boxes, as she had been advertised as a prostitute.
"By this time, I was broken," she says. "I couldn't sleep, couldn't eat, I lost two stone. I was shaking, I couldn't drive." Over a six-month period, she was interviewed for 25 hours by the HR manager and the assistant headteacher. One meeting lasted for almost five hours.
"To this day, I still do not know what I did as it was never outlined. Even the HR manager said no one could really say what it was they took such exception to. I stood no chance. I've been told the person who investigated complaints now does my old job, which has raised many eyebrows, but not mine. For me, it makes a sense out of what was nonsense," she says.
The situation became so bad that one teacher resigned, disgusted at the treatment that Mary had received. "I have never witnessed a witch hunt like it," she wrote in her resignation letter. Two other teachers left as a result; and during the hearing, two of the nine individuals involved apologised to her and two backtracked on previous statements.
"I felt confident the truth would out, and it didn't," says Mary. "I still dream about the hearing. I'm fighting back and now saying everything I should have said and couldn't."
Mary's case is by no means an isolated incident. The UK National Workplace Bullying Advice Line estimates that about 20 per cent of all calls it receives are from teachers, lecturers and individuals working in education; making this the largest group of more than 10,000 cases to contact the helpline.
In May, Keith Waller, 35, a teacher at St Lawrence Primary School in Essex, hanged himself. Constant pressure and questions over his ability to teach led him to commit suicide, an inquest heard last month. In June, Vanessa Ran, a teacher from Bristol, was found hanged after a colleague allegedly slapped her face in front of her class.
Although suicide is not common, most teachers who are subjected to a school disciplinary process or bullying by colleagues suffer health problems as a result. "It just happens; you wake up and you can't do it," says Liz, a primary teacher in the North-west. Her experience of workplace bullying led to her being signed off with serious health issues earlier this year.
After a series of incidents in which her headteacher publicly undermined her ability to teach, Liz fell ill and was signed off from work for a week by her doctor. When she tried to return to the classroom, the school secretary and the HR manager, under directions from the headteacher, tried to block her from doing so.
This was just the beginning. Over the next 12 months, Liz felt increasingly victimised, when applying for management posts and while teaching. Eventually it became too much, and despite having an excellent teaching record, she has been signed off work with stress since July.
"You go home and you cry, and the next day you wake up and you can't do it," she says. "I want to go back into teaching, but I can't. I love the kids, but I can't go back."
Liz is submitting a grievance against her school, but she is too ill to work and doubts she will return to the classroom.
If you're the victim of a sustained campaign that questions your ability and personality, it's very difficult to emerge unscathed, says Mary. You may eventually begin to believe the accusations, so speak to a therapist, talk to friends and family, and remember that it is very often just the opinion of one or two individuals that is the root of your self-doubts.
"The most important factor is not to get so ill that you lose your ability and your will to fight against what you believe is corruption," says Evelyn, an ex-teacher and consultant. "If you search your heart and still find what has happened to you to be unfounded, stand up and refuse to accept this miscarriage of justice. You will leave the school, but how you leave will determine your recovery."
"Most of the complaints against me were that I was rude, had poor communication skills and was incompetent. Bullies project this on to you," says Liz. "You must be clear in your mind that you aren't." Be careful who you trust, Liz advises: "Don't talk to other people, because your friends fall away from you. They're afraid."
This, perhaps, is hardly surprising, given the treatment Liz received for complaining about her headteacher to the governing body. Why, then, risk ostracism from your colleagues? "It's your duty to speak up," she says, although she can see why other staff were too terrified to support her.
Sadly this lack of support from colleagues is what allows the situation to develop, says one teacher who asks not to be named: "This will carry on until as a profession we collectively do something about it," he says. "The trouble is that often the staff at closest quarters who could help and witness these incidents develop blinkers and see their own safety as the main issue. They will conveniently turn a blind eye to another's bullying. Unless, of course, the bully targets them, and then there is no one to give them the support they need."
However, Evelyn says it's crucial to make the issue of school bullying more apparent: "People have to share accounts of what's happened to them. Once the problems are widely recognised, current policy has more chance of being evaluated and positive change can be effected carefully but definitely."
"I want local education authorities to recognise that these procedures are so easy to manipulate," says Mary. "More people have to fight. I want to see independent investigators, trained in employment law and with the motivation to out the truth, not protect the school. I want to hear that malicious or trivial or unbelievably cruel allegations get highlighted and thrown out for what they are.
"I was given a glowing reference but will never need it. I will not be returning to this work. I was described by the DfES, the Home Office and my previous employers as an innovator. This fact did me no favours. It does not pay to be described as better than the rest. The resentment it causes in others will destroy you - this has to stop. I pray it does."
Names have been changed
What to do if you're accused
Make sure you have every accusation in writing.
Contact your union and a solicitor specialising in employment law. Your union may have a hardship fund to help with costs and a solicitor can offer unbiased legal advice.
Get a copy of your school's grievance and disciplinary procedure, and make sure it's being followed.
Do not discuss this with other staff, as confidentiality is paramount. Do, however, bring someone to your first meeting to act as witness. This can be either your union representative or a colleague.
Take your own minutes. Pass these on, along with the minutes from HR or the Senior Management Team (SMT), to your union and solicitor - they will probably differ. Do not accept the minutes until you agree with them.
Do not resign before the hearing, even if the SMT has advised this, unless you and your solicitor have agreed to as part of a compromise agreement.
If you don't agree with the outcome of the hearing, appeal against the decision. You should have 14 days to do this.
If you submit a grievance, send it to the person responsible for all governors within the LEA. If you send it directly to the school, the headteacher will probably open it.
If your solicitor advises going to a tribunal, do it.
Stop worrying about your future employers and stop feeling guilty.
A head's defence
Having been a real teacher once, I empathise with my staff (I was also a teaching assistant, so I empathise with them too).
However, none has been a headteacher and cannot in the remotest understand what I do. We don't have time for conspiracies, or the energy. I could count on the fingers of one finger the number of times headteachers of my acquaintance have bragged about how many staff they just "got"... We just can't. There are too many legal constraints, and a good thing too.
It is very easy to criticise, but the next time you ask your headteacher what seems to be a simple question, and they seem distracted, or maybe do or say something that you feel is more than faintly ridiculous, ask yourself: what else is going on here? And then remember, whatever it is, it is in addition to worries about Ofsted, HMI and responses to the Government's latest crackpot strategy. And if you can consider these things, and maintain a little bit of balance, then you are a better man than I am.
Stories told online
Teachers have been sharing their experiences of workplace bullying on The TES website
Ruined, destroyed and damaged: why schools are breaking staff www.tes.co.ukblogsblog.aspxpath=Speakers'%20Corner02%20Archive02%20October%202007
Bullied in school? Fight back
Thread in the staffroom www.tes.co.uksectionstaffroomthread.aspxstory_id=2452043path=OpinionthreadPage=messagePage=1
www.bullyonline.org Offers support, advice and guidance for teachers who feel bullied.
For excellent broad advice including mediation (waiting lists are long for mediation).
Here you can download valuable information from the Citizens Advice Bureau.
You can sign a petition requesting a fairer deal from headteachers.