Just one day before the stabbing, Noel’s father was so worried about the threats to his son that he visited the principal at Intermediate School 117, asking for a “safety transfer,” said Marisol Perez, a neighbor and close family friend.

But with only a few days left in the school year, Mr. Estevez was told to have Noel identify the people causing him problems and was assured that the school would look out for him.

Carmen Fariña, the schools chancellor, said that the case was under investigation and that she was troubled by what happened.

“I haven’t slept well since last night,” she said on Thursday during a visit to a school, according to a transcript provided by the Education Department. “The reality is that this is something that shouldn’t happen. Certainly shouldn’t happen to 14-year-olds. I’m devastated.”

Mr. Estevez’s plea to the school was not the first time the authorities had been warned of the conflict. At various points in recent weeks, the school, the Administration for Children’s Services and the Police Department were informed of the brewing tensions, according to accounts from neighbors and family friends.

For months before the stabbing, Noel had been under attack by Timothy and a group of his friends, according to witnesses.

And it was not just during school that he was tormented.

The boys would show up at Noel’s apartment, hurling abuse and even going so far as to urinate on the door of his family’s apartment on East Clarke Place in High Bridge.