A former school business manager, also referred to as a bursar, has claimed she was unfairly dismissed.
During an employment tribunal, Diane Harcourt alleged that she was forced out of her role at the Green School for Girls after complaining about the management of the headmistress Pam Butterfield, the Hounslow Chronicle reports.
The 55-year-old lost her job in January of this year, six months after receiving her final warning.
She told a hearing in the south London commercial centre of Croydon that she had suffered insomnia, swollen joints and nausea as a result of being "victimised" by her boss.
Ms Harcourt also claimed that she had been "severely reprimanded" for suggesting that Ms Butterfield had claimed too much in consultancy fees.
The head teacher, however, denies the allegations and accuses her former bursar of failing to carry out her duties as a member of the school's senior leadership team.
A ruling on the case is expected in around a month.