Charges of common assault against Judi Sunderland were dropped this week, after the prosecution admitted that medical evidence did not support the pupil’s version of the incident.

Mrs Sunderland was charged with assault after holding the arms of a 13-year-old boy who was abusing and kicking out at her. She said: “Whenever I go to the doctor or dentist, there are signs telling you not to abuse the staff. But in school, teachers locked themselves in classrooms to avoid confrontation with pupils.”

Mrs Sunderland began working as health and social-care teacher at Immanuel community college, Bradford, in September 2003. The incident took place in December, and she was suspended in May 2004, after several months of sick leave.

The 1,200-pupil comprehensive was placed in special measures in January 2004. Inspectors criticised the behaviour of pupils, saying that they were “lethargic and lacking in motivation”. Mrs Sunderland claims she was assaulted by pupils six times, resulting in a black eye and a sprained thumb.

“I came to Immanuel because I wanted to make a difference,” the 56-year-old grandmother said. “I was altruistic. But that’s the last time. People ask me, would I do the same thing again? I don’t know. I’m beginning to doubt my professional judgement, and that is very sad.”

Mrs Sunderland is now waiting to hear from the school, and will take advice from Bev Marshall, regional officer for the National Union of Teachers. Mr Marshall said: “The law allows teachers to restrain a pupil, if the circumstances are appropriate. Our concern is that teachers will now feel afraid to take this action.”

Tony Thorne, who was appointed executive head of Immanuel after it was placed in special measures, said its atmosphere has improved dramatically over the past 18 months.

He said: “A huge amount of good work is being done. The new leadership team has introduced significant changes, which are acting as a springboard for a successful future.”