One of New York City's most prestigious private schools has apologised for more than three decades of sexual abuse committed by teachers and administrators.

A letter on its website apologises for the abuse at Horace Mann School between 1962 and 1996.

"We sincerely apologise for the harm that was caused by the teachers and administrators who abused anyone during their years at Horace Mann School," board chairman Steven Friedman and head of school Thomas Kelly said in the three-page letter.

"These unconscionable betrayals of trust never should have happened."

The Bronx district attorney's office and the New York Police Department launched an investigation into allegations of abuse at the school after a New York Times Magazine article last summer that said the academy was plagued by teachers who sexually abused children in the 1970s.

In April prosecutors said that while there was a systemic pattern of suspected sexual abuse at the Bronx school, the statute of limitations to prosecute them had expired.

In the letter, Mr Friedman and Mr Kelly said the school had hired a private mediation firm which presented the board of trustees with impact statements from 31 people who described their abuse.

They said settlements have been reached with "the great majority".

Mr Friedman and Mr Kelly said the school's board would eliminate a position of trustee emeritus and create an advisory board on pupil safety, which may include a victim of sexual abuse.