But critics say that the firms, often described by administrators as “independent,” can be too close to the schools they are investigating. Ultimately, it is the schools that pay their bills, and decide what information will be released.

“If they do this full time, there is a perception issue, that they’re not going to draw tough conclusions in all cases,” said Roderick MacLeish, a lawyer who represents victims of abuse at private schools. “If you’re going to keep doing this, how tough are you going to be on some private school client, when you are basically marketing yourself for other investigations in the future?”

Even the firms that conduct them acknowledge that the investigations are not free of conflict.

“It’s important for institutions to be careful about the word ‘independent’ and be transparent about what this means,” said Paul G. Lannon Jr., a partner at Holland & Knight. “They are paying for these services, it’s not like these are volunteers coming in.

“But they are professionals coming in with professional experience,” he said. “They are members of the bar who are obligated to comply with ethical standards, rules of professional conduct, of behavior — and to seek the truth. Absent a better alternative, this is probably the best the schools can do.”

Investigators also acknowledge that there are limits to their work. They are private lawyers, not law enforcement, and they cannot compel people to participate by issuing subpoenas. Often, investigators are working with limited records from long ago, and contacting alumni using addresses schools have on file. As a result, many survivors — and perpetrators — are left out.

Schools often discuss the reports in terms of their obligations to victims and the larger community, and many survivors and their advocates welcome the more thorough reports. Sexual abuse survivors from Horace Mann School in the Bronx say they have been asking the school for years to commission an independent investigation, which the school has declined to do.

“We want the validation of an independent third party looking objectively at the facts and saying, ‘Yes, I believe this happened to you, and here’s my understanding of how it happened,’” said Joseph Cumming, who said he was abused at Horace Mann in the 1970s. Horace Mann did not respond to multiple requests for comment.