Rosemary Powell, Kristin Watkin and Dianne Elliott, who worked at Ashlawn school, Rugby, have all lodged constructive dismissal claims against Warwickshire County Council.
Mrs Powell, 60, who was the school's secretary for 18 years, told an employment tribunal she was hounded out of her job by 51-year-old headteacher Peter Rossborough and senior management.
She claimed Mr Rossborough stared at her at work and made her feel intimidated and frightened, and that senior staff had excluded her from conversations.
Carolyn D'Souza, for the authority, said Mrs Powell had rejected an "olive branch" offered by one of the managers and had failed to notify governors exactly how she felt. The case was adjourned until July.
Former modern languages teacher Kristin Watkin, 54, told a second tribunal she was harassed and intimidated by Mr Rossborough until she had a breakdown.
She described working at the school under Mr Rossborough as "like living in a police state".
Mrs Watkin, a mothr of three, resigned from the 1,450-pupil school in 1998 and has not worked full-time since.
Her case was adjourned until next month and will not conclude until September.
A third case, in which business studies teacher Dianne Elliott will claim constructive dismissal on the grounds that she was victimised by Mr Rossborough, will be heard in October.
Two months ago, Eric Wood, Warwickshire's county education officer, wrote to Mr Rossborough offering his "unreserved" support and assistance.
He said Ashlawn was one of the finest schools in the county and that he had been surprised and saddened at the allegations made against Mr Rossborough.
Mr Wood said that it was extremely difficult to find headteachers of the calibre of Mr Rossborough, a former Coventry rugby union captain, who was capped seven times for his country in the 1970s.
"I have nothing but admiration for your professional, caring approach and the excellent manner in which you head the school," he added.
Mr Wood told The TES this week he stood by his position. He said: "It would be quite inappropriate to make any kind of judgment on the basis of what has been heard so far in the tribunals."