BOSTON » A former Massachusetts attorney general has been hired to conduct an independent investigation into allegations of sexual abuse at a prestigious Rhode Island boarding school.

More than 40 former students at St. George’s School in Middletown have alleged they were molested or raped there, mostly in the 1970s and ’80s.

Last month, the school said an investigation found 26 students had been sexually abused by six former employees and several former students. The school acknowledged it didn’t report abusers to authorities at the time and apologized.

The school agreed to do a new investigation after many victims questioned the impartiality of the first one, which was led by the law partner and spouse of the school’s attorney.

The school and a group of victims announced Monday that Scott Harshbarger, who also was a Massachusetts prosecutor, has been hired to conduct the new investigation.

The two sides also said they have agreed to an independent program for providing mental health services to the victims. People who were sexually abused by faculty, staff or students at St. George’s can receive crisis mental health assistance or referrals to local mental health professionals by contacting Day One of Rhode Island, a nonprofit provider of services for victims of trauma.

The services will be paid for by the school. The names of alumni receiving mental health assistance will not be revealed to the school.

Rhode Island state police also are investigating the sexual abuse allegations.