The principal of elite Sydney girls' school, Kambala, has resigned and will not return to the school after parents and teachers mounted a campaign to have her removed, just 3½ years after her appointment.

In a letter to parents on the first day of the school holidays, the president of the school council, prominent businesswoman Sally Herman, said Debra Kelliher had resigned and would "conclude her time at Kambala immediately".

"Debra has done a wonderful job in her three-and-a-half years at Kambala," the letter, sent on Monday morning, said.

"She leaves a legacy focused on the key areas the council identified on her appointment - the school's academic results have improved significantly, enrolments have increased to their highest ever level, the school is in an excellent financial position."