A dozen former teachers at an elite Connecticut boarding school were named in a report Thursday that detailed decades of alleged sexual abuse against students. The report, prepared by an investigator working for the Choate Rosemary Hall boarding school, details sexual misconduct that allegedly occurred from 1963 to 2010, according to a letter from Michael J. Carr, the head of the board, and headmaster Alex Curtis. The report relied on testimony from 24 former students, with incidents ranging from kissing to forced sexual intercourse. One of the more shocking allegations describes a 17-year-old female student forced to have sex with a male teacher in a swimming pool while on a school trip to Costa Rica, the report said. Three students who witnessed the assault corroborated the story, according to the report. But in that and other alleged incidents, school officials failed to notify authorities and instead quietly forced the accused teacher to resign, the report said. The teacher in the alleged swimming-pool rape went on to work at other schools. “The detailed content of this report is devastating to read,” a letter from school administrators that accompanied the 50-page report said Thursday. “One can only have the greatest sympathy and deepest concern for the survivors. The conduct of these adults violated the foundation of our community: the sacred trust between students and the adults charged with their care,” the letter said. Choate, which counts former President John F. Kennedy and playwright Edward Albee among its alumni, has set up a fund to help the victims of sexual misconduct at the school get therapy.