A senior member of the teaching staff at one of Sydney's top private schools has been charged over the alleged sexual assault of a female student.

Detectives investigated reports a teenage girl, then aged 17, was sexually assaulted by a male teacher in 2018 at Reddam House in Bondi, a police spokeswoman told AAP on Tuesday.

Ben Fenner, 34, was arrested on July 19 and charged with 11 counts of sexual intercourse with a person under his care.

He was granted strict bail to appear at Downing Centre Local Court on August 26.

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The accused, who was part of the senior teaching staff at Reddam House, has been stood down from all duties, a school spokesman said in a statement.

"We are most distressed by this turn of events and want to assure parents, students and all in the school community that Reddam regards this matter extremely seriously," the spokesman said on Tuesday.

"Pending resolution of due legal process, the teacher involved will not play any further role at the school.

"This is now a matter for the court."