An elite all-boys private school in suburban Maryland revealed that seven of its alumni have reported sexual abuse by a longtime teacher, more than 50 years after the alleged acts.

Leaders at the Landon School said that the fifth-grade teacher — Ward Bates, who died in 2011 — was accused of repeatedly sexually touching the students or leading them to touch him while he taught at the Bethesda school. He was an instructor there from 1946 to 1962.

“The reports were highly credible and similar in many disturbing respects,” Headmaster Jim Neill and Board of Trustees Chairman Scott Harris said in a joint letter to the Landon community Thursday.

The alleged misconduct mostly took place in classrooms, but some was reported outside of school, the letter said.

The accounts follow an investigation that started in late 2017, when two alumni came forward with personal stories about Bates. Landon hired an outside firm to investigate, T&M Protection Resources, which spoke with 26 people.

“Words do not suffice to describe the great sorrow and anger we feel in learning of this abuse,” the letter said. “Parents place their faith in educators to keep their children safe, but these boys — now men in their 60s and 70s — have lived with these memories for decades. No child here or anywhere should experience this kind of horrific mistreatment, and we again extend to these men our sincerest remorse and apologies.”

Landon, which enrolls 670 students from third to 12th grade, said in the letter it had no evidence that Landon’s administration was aware of alleged abuse at the time it happened. The victims were in fifth grade.

But one graduate who reported abuse by Bates said a school official was told in 2007. Landon leaders said they could not be certain who was contacted.

“Despite the lack of clarity around this 2007 report, we can say that steps should have been taken by the school to investigate and report on the issue at that time, and we apologize that they were not,” the letter said.

The school said Bates worked as a summer counselor at Camp Wachusett in New Hampshire and later taught at the Blake School in Minnesota. Landon shared findings of the investigation with both, the letter said.

The school said a task force of former and current board members worked with investigators to consider questions around naming the accused teacher. It based its decision to do so on factors including multiple credible firsthand accounts and the severity of the behavior.

While it named Bates, it did not name another long-deceased faculty member accused of sexual contact with a student off campus in the 1970s. The report was credible, but the name was not released because it was a single report, the letter said.

No reports of sexual misconduct were made about the school’s current staff, it said.

School leaders said the Landon task force worked with lawyers to ensure it is complying with laws about reporting incidents to child protection agencies, the letter said.

Police said they were not involved.

“The police department did not receive any information from the Landon School regarding this matter and the school’s investigation,” said Sgt. Rebecca Innocenti, a Montgomery County police spokeswoman.

Meredith Josef, a Landon spokeswoman, said the school “explored all avenues for involving the authorities. However, because Mr. Bates was deceased, we focused on assisting the survivors.”

The school said it is continuing staff training and student education about appropriate behavior by adults. In late 2017, it formed a safety committee to evaluate school practices. Background checks are done on an ongoing basis, not just upon hiring.

Dan Morse contributed to this report.