Through a spokeswoman, Fordham Prep’s president, the Rev. Christopher J. Devron, said that after the first death, the school set up a counseling center for students and held a meeting for faculty members, led by the school’s counselors, to help teachers recognize signs of emotional distress.

On Tuesday, he said, the school also hired Amelio A. D’Onofrio, a 1981 graduate and the director of the Psychological Services Institute in the Graduate School of Education at Fordham University, to assist Fordham Prep. He said Dr. D’Onofrio, who has an expertise in adolescent self-injury, would counsel students and hold a meeting for parents.

Meredith Daniels, a spokeswoman for the Metropolitan Transportation Authority, which operates Metro-North, said that, for now, the agency was posting police officers on the platforms of stations serving Fordham Prep students when they were coming and going from school.

At least five communities in the United States per year experience a youth suicide cluster of three or more suicides, according to Madelyn Gould, a professor of epidemiology in psychiatry at the Columbia University Medical Center, who is an expert in the topic. Teenagers and young adults are particularly susceptible to what is called suicide contagion, Dr. Gould said, possibly because of the role that peer relationships play in their lives, or because of their impulsivity.

She said the second student suicide at Fordham Prep was almost certainly an instance of imitation, with the deaths so close in time and in the same manner being “more than just a coincidence.”