A former Catholic school teacher and summer baseball league coach was ordered yesterday to serve three months in the Montgomery County jail after he pleaded guilty to fondling a 15-year-old former student and showing him Internet pornography.

Glen Mayers, 31, of Silver Spring, also was ordered to serve three years of probation, during which he must continue therapy and not have contact with children younger than 16 without another adult present. The remaining 15 months of an 18-month jail sentence was suspended.

Mayers, a former seventh-grade math and science teacher at St. Camillus Catholic School in Silver Spring, apologized to Montgomery Circuit Court Judge DeLawrence Beard and faced the youth, who sat in the front row of the courtroom with his mother.

"I'm very sorry, pal," he told the teenager. "I never, ever, ever wanted for this to happen. I'm sorry you had to come into my path . . . You're a good kid, and I know you're going to be all right."

Mayers told the judge that he, too, had been sexually abused as a child and that he was "devastated" knowing he likely would never teach again.

But Beard told Mayers that he had violated a sacred trust, both that of a teacher with his students and the trust of a "particularly vulnerable" student.

"You were the adult," Beard said. "You had the responsibility to control the situation."

Mayers was accused of sexually touching the student and showing him pornography on his St. Camillus classroom computer in February, when the student, who had already graduated to high school, returned to help Mayers in his classroom.

Assistant State's Attorney Kristen Bender said Mayers had told a therapist in 1993 that he knew he "fit the profile" of a child abuser yet still sought close contact with children. She said Mayers sought out the youth, whose father had recently died, because he was particularly vulnerable and paged him in the middle of the night to talk to the student about sexual topics.

Bender said she was not surprised by the several parents and fellow teachers who came to Mayers's defense and called him an excellent teacher and coach who would never intentionally harm a child. Mayers coached summer baseball in the Babe Ruth League in Prince George's County and worked as an assistant junior varsity baseball coach for three years at DeMatha Catholic High School in Hyattsville.

"It's that same charm," Bender said, "that turns into manipulation with a child."