(CNN) An investigation into allegations of sexual misconduct at a group of schools associated with the Washington National Cathedral that was made public Thursday found that 16 adults formerly connected to the schools or the cathedral had committed sexual misconduct against students.

Most of the cases corroborated by the investigation, which was conducted by a private law firm at the request of the religious leadership of the schools, took place between 1950 and the early 1980s, the report says, with the most recent corroborated incident in 2008.

Most of the allegations detailed in the report resulted in forced resignations at the time, but some cases were "handled less decisively" than current school leadership says is standard practice.

The investigation adds the capital's Episcopal population, and the nationally renowned neo-Gothic cathedral at its center, to the list of communities reckoning with sex abuse scandals.

In a letter sent this week to parents of current students, former students and parents of former students, Rt. Rev. Mariann Edgar Budde, the bishop of the Diocese of Washington, apologized to the victims of the abuse and promised to "make tangible and sustained efforts to continually evaluate and, where appropriate, strengthen the safeguards that, thankfully, are already in place."

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