I had been falsely accused once before when I put two Year 7 boys in detention, but that passed over pretty quickly. They felt aggrieved and one told the deputy head that I had hit him in class. I thought it was a joke at first. Most of the class spoke up and said it wasn't true. No more was said, but I was surprised that the boy went unpunished.
The next time I was accused, about nine years later, it was far more painful and protracted. It was the first term in 2006. I had been teaching at the same comprehensive in Hertfordshire for 17 years and it was the year before I was due to retire.
The school was running a correct uniform campaign and I was standing by the door as my registration group filed past, telling them to tuck in their shirts, or whatever it happened to be.
I told this one 12-year-old girl to do her tie up and button up her shirt. She refused and started to be verbally abusive. She tried to get past me and I put my body in front of the door to prevent her from leaving.
I didn't touch her but there was quite a bit of manoeuvring from side to side as she tried to get out and I tried to keep her in. Eventually she pushed me out of the way and ran downstairs to reception to ring her mother. I had another class so thought I would deal with it later.
The girl told her mum that I had pushed her up against a cupboard. The reception ladies overheard and soon the headteacher was involved. I was sent for by the head and he told me that I had been accused of physical assault. He was sympathetic, but was obliged to take the allegations seriously.
There were no witnesses this time so it was my word against hers. I was in a total state of shock. I couldn't believe that one girl who really wasn't very able or articulate could ruin, if not my career, then my reputation. I was coming up to retirement age and I thought I might not get my pension. And I felt for other younger members of staff who might be falsely accused. Their whole career could be ruined by a lie.
The seriousness escalated when the girl's mother involved the police. I was in a terrible state by then and became quite tearful. Neither the police nor the school could find any evidence to support the girl, but there was nothing to disprove it either.
I was not suspended from duties and tried to carry on teaching as best I could, although it was hard to concentrate. I refused to be in contact with the girl so she moved form and teaching group.
After an agonising two weeks, the case was dropped, but I was still worried that my colleagues would think there's no smoke without fire. I hoped they knew me well enough to know that I was innocent, but I couldn't be sure.
In fact, when I discussed it with them, they were incredibly sympathetic. It emerged that several colleagues had been falsely accused by other pupils but there was a culture of silence so no one really knew about it. Greater openness would help so much: having someone you know and respect say, "This happened to me, too, so don't worry."
Talking to colleagues, I realised that this family was well known to the school and that the girl was well practised at inventing things. One of the teachers had taught her mother, who apparently was even worse.
I was amazed that the perpetrator again went unpunished. I, meanwhile, felt somehow ashamed and tainted. I started to doubt myself and wonder whether I did push her after all. I also felt guilty for taking up so much of the head's time.
Now that I have left teaching, I wonder whether the girl had started to believe her own lies. I have heard that she has since been permanently excluded for another offence. I don't feel sympathy or pity for her - just anger, disgust and frustration that there was no procedure in place for punishing her. My reputation, meanwhile, had been irreparably tarnished.
As told to Hannah Frankel. Do you have an experience to share? Email email@example.com.