Joan Sherry, an RE teacher who worked at Trinity school, Carlisle, is accused of talking to pupils about her difficult relationship with Mike Gibbons while he was headteacher - telling them he did not like her.
England's General Teaching Council heard that four years ago she left a class unattended so that she could go to a local police station to make allegations against Mr Gibbons and the 1,800-pupil school.
Mr Gibbons, giving evidence at the GTC hearing in Birmingham last week, said: "As a result of her behaviour the school was at the centre of speculation and attention, which had a destabilising effect."
The committee heard police took no action. However, they rang the school and told Mr Gibbons that she had ranted about the school and that they could not believe she was a teacher.
Mr Gibbons said: "I had a telephone call from a very apologetic police officer. I found it troubling and embarrassing. Hers was a serious criticism of the school to another civic institution in the city."
Mr Gibbons said Ms Sherry had gone to the police after being intimidated by a student. The pupil was due to be suspended and an investigation was being carried out. The student had made a counter-allegation and Mr Gibbons felt it was his duty to investigate the pupil's claim.
He said Ms Sherry told the police that the school was not doing enough to protect her from students and that she was being investigated rather than the student. Mr Gibbons believed that Ms Sherry had acted in an unprofessional manner by storming into his office and refusing to behave civilly over the investigation.
During the summer term of 2001, it was alleged that pupils and staff knew Ms Sherry was planning to take sick leave until Mr Gibbons left the school.
Ms Sherry also instructed her mixed class of 12-year-olds to draw a circumcised penis as part of their homework, the GTC heard.
She admitted instructing the pupils to do the drawings but said she did not consider it inappropriate as the diagram came from a text used in personal, social and health education lessons, rather than religious studies.
But the GTC was told parents of Year 8 pupils complained and that Ms Sherry's head of department did not regard such drawings to be part of the work scheme.
Ms Sherry, 48, now works for the court service in Carlisle. She taught at Trinity from 1986 until 2002 when she was dismissed.
The GTC hearing was adjourned and will be reconvened to consider further evidence at a later date.