One woman approached the school with a report about him, which was passed along to a law firm the school employs to “fully investigate her concerns,” a spokeswoman for Andover said in an email. Andover declined to provide details on the allegations.

A second woman, who attended Andover’s summer session in 1980, brought her account to The New York Times. That woman spoke on the condition of anonymity as a victim of sexual misconduct.

The woman said that Mr. Lyman had given her alcohol, and that they had held hands and walked with their arms around each other. He tried to kiss her. She had been flattered that her teacher had taken an interest in her, she said. On a group camping trip, the student woke up in the middle of the night to find Mr. Lyman kissing and stroking her arms. She said she had pretended to be asleep.

“It would have been so easy for things to happen, but I drew the line,” she said.

“He groomed them,” she said of young women at Choate with whom Mr. Lyman is said to have engaged in sexual relationships. “And if I had been with him for longer, he may have groomed me, too. I was only there for six weeks.”

Andover said that Mr. Lyman was a teaching fellow at the school during the 1978-79 academic year, and that he taught at the summer session in 1979. A spokeswoman said that because the school had “limited records” of who taught at summer sessions during that time, it could neither confirm nor deny that he was on the faculty during the summer of 1980.

Jan Thomas, a spokeswoman for Kent Denver, said Thursday that the school had no knowledge of Mr. Lyman’s issues at Choate until contacted by a reporter last week, and that there was no evidence that he had engaged in “physically inappropriate” behavior at Kent Denver, she said. He left the school, and education, in 1984, after two years at the Colorado school.

Then, on Friday, Rand Harrington, the head of school at Kent Denver, sent an email about Mr. Lyman and sexual abuse to members of the school community, including alumni. The school received a response that evening, Ms. Thomas said, but she would not say whether Mr. Lyman was the subject of the response, citing confidentiality.