The alleged victims, all alumni of St. George's School in Rhode Island, had previously criticized the school's response to the allegations
and had demanded an impartial investigation in a news conference on Tuesday.
Anne Scott, a member of the class of 1980 who says she was raped by a former athletic trainer at the school, reacted on Thursday: The "decision is a very important first step in what we hope will be a process of reconciliation and healing."
The investigation, by an independent party to be chosen by the school and the victims, "will not be limited in scope or time period and will be conducted in a manner sensitive to victims who may have already provided information," St. George's said in a statement.
At least 40 people claiming they were abuse victims have come forward as a separate investigation by the Rhode Island State Police continues.
St. George's, an Episcopalian school overlooking the Atlantic in Middletown, issued a report to alumni last month after its own investigation expressing "regret, sorrow and shame that students in our care were hurt" and saying that it "failed on several occasions to fulfill legal reporting requirements."
"From the school's perspective today -- and as almost all victims and numerous other witnesses indicated -- we believe the School could have done more to keep its students safe," the St. George's report said.
Leslie Heaney, chair of the St. George's School board, said the board is "committed to a truly impartial investigation."
"There is nothing more important to us than that the review be thorough and exhaustive, and that its findings are found to be reliable and credible by all parties, particularly the victims," Heaney said.
In its report, the school said its nearly yearlong investigation discovered 26 "credible first-hand accounts (as well as other corroborating evidence) strongly suggesting that three former employees of the school engaged in sexual misconduct with regard to multiple students, and that there were twenty-three victims of sexual misconduct by these three employees."
Representatives of St. George's School attributed the discrepancy in the number of victims to the fact that additional victims came forward after the school released its investigative report last month.
'We are truly, deeply sorry'
The school did not report the incidents to authorities at the times of the abuses but contacted the Rhode Island State Police last fall after completing its investigation.
Attorney Eric MacLeish, who represents a group of the victims, said on Tuesday his clients have identified seven individuals who worked at the school who are alleged perpetrators of sexual abuse; four of them, he said, remain alive and could face prosecution.
Four former school employees were fired, the school's report said. One staff member was fired for giving alcohol to students, but the sex abuse allegation did not surface until the school's recent probe.
Rhode Island State Police Capt. Matthew Moynihan said police launched an investigation in November after being contacted by school officials.
"To all victims, we are truly, deeply sorry for the harm done to you by former employees or former students of the School," the St. George's report said. "We are heartbroken for you and for the pain and suffering that you have endured."
The school has offered to pay for therapy for the victims, the report said. It also set up a victims fund for therapy and other treatment and to reimburse victims for past treatment.