CONCORD, N.H. — A New Hampshire teacher has been charged with trying to hide a relationship with a student at his previous job at an elite prep school that’s being investigated for sexual assaults by teachers on students.

David Pook, 47, of Warner, New Hampshire, was arrested on witness tampering and conspiring to commit perjury charges following a grand jury investigation into misconduct allegations at St. Paul’s School in Concord. The office began its investigation last summer after St. Paul’s put out its own report about sexual assaults by teachers and information about the “senior salute,” a game of sexual conquest that led to the conviction of St. Paul’s graduate Owen Labrie in 2015.

Attorney General Gordon MacDonald said Pook taught at St. Paul’s for eight years but left “under questionable circumstances” in 2008. He’s been at the Derryfield School in Manchester, New Hampshire, since 2009, where he taught history. Derryfield said it suspended Pook on Wednesday and that the charges don’t involve any of its students.

Pook is scheduled to be arraigned on March 15. A phone number and email address for him weren’t working, and it wasn’t immediately known if he has a lawyer. A message was left for a lawyer who represented Pook when he was called before the grand jury in December.

St. Paul’s rector, Michael Hirschfeld, said Pook was a humanities teacher who was “separated” from the school after he “violated school rules governing boundaries between faculty and students.” Hirschfeld said there was no evidence of a sexual relationship between Pook and a student.

“The school leadership at the time should never have given Mr. Pook a recommendation and the fact that it did not inform Derryfield of Mr. Pook’s boundary issues was a failure for which we apologize,” Hirschfeld said in a statement.

Court documents show records subpoenaed from St. Paul’s revealed “several troubling incidents” involving Pook — the male head of house in a girl’s dorm — that made the students uncomfortable, such as entering their rooms when they were getting ready for bed. Pook responded by expressing “concern about being able to visit girls at all hours of the night” if he was to do his job.

According to court paperwork, a student testified before the grand jury she believed a friend was having a romantic relationship with Pook and that they had been exchanging emails.

The friend appeared before the grand jury in November and testified that she never had any sexual contact with Pook. She also testified she hadn’t had any contact with him since receiving her subpoena.

But investigators said he obtained phone and email records showing that she and Pook were in frequent contact with one another leading up to their testimony, and that Pook pressed her to give him details of what she would say.

The investigator also said it is “clear” from his review of the emails that the two are in a sexual relationship and have been for some time.