For years, the school kept allegations of sexual misconduct from getting out, according to the report. “Sexual misconduct matters were handled internally and quietly,” it said. “Even when a teacher was terminated or resigned in the middle of the school year because he or she had engaged in sexual misconduct with a student, the rest of the faculty was told little and sometimes nothing about the teacher’s departure and, when told, was cautioned to say nothing about the situation if asked.”

Image Cheyenne Montgomery with her teacher Björn Runquist at a school event in 1992. She later said he abused her. Credit... Cheyenne Montgomery

Cheyenne Montgomery graduated from Choate in 1992, and as a student there, she said she was abused by two teachers. In a telephone interview, Ms. Montgomery described herself as an unusual Choate student because she had very little money. The Times does not usually identify victims of sexual assault by name, but Ms. Montgomery wanted to share her story publicly.

Angus Mairs, a math teacher, encouraged students to come to him for extra help, she recounted, and during her sophomore year, he suggested that she visit him to study.

“Conversations with him started getting more personal,” she said. “He started kind of sharing information about himself and digging into information about me, mostly about my father, and kind of through that, it developed into what felt to me like a boyfriend-girlfriend situation. And it became physical.”

Mr. Mairs left Choate at the end of the school year.

During Ms. Montgomery’s senior year, she said, she was abused again, this time by a French teacher, Björn Runquist, whom she had told about the abuse she suffered at the hands of Mr. Mairs. Shortly after she graduated, Choate learned that the two had an inappropriate relationship, though the report says administrators were unaware that the relationship was sexual. The report said this prompted Mr. Runquist’s exit from the school at the end of the academic year. He “then returned to the Kent School, where he had taught before joining the Choate faculty, and from which he retired in 2013.”

Ms. Montgomery recounted her experience in the 2016 Boston Globe article.

As recently as 2010, a longtime faculty member named Charles Timlin kissed a student and made inappropriate sexual comments to her, the report said. Edward Shanahan, the headmaster at the time, is quoted as saying that Mr. Timlin had been a “25-year faculty member, great teacher, great coach, great faculty member,” and Mr. Shanahan decided that the conduct did not warrant his dismissal.

Mr. Shanahan said Mr. Timlin could stay on at Choate if he saw a psychiatrist and moved out of the girls’ dorm, where he worked as an adviser. He was also required to sign a letter of resignation, which could be used if any other accusations came to light or if the episode with the student “became more of a public matter.” In the fall of that year, the student’s father contacted the school, after which the school informed the Connecticut Department of Children and Families and dismissed Mr. Timlin, though he was paid through the end of the academic year. Mr. Shanahan could not be reached for comment.