“Allegations of abuse against a helpless, innocent child are even more horrific and disturbing when the crimes are committed by someone who is meant to protect the child,” Darcel D. Clark, the Bronx district attorney, said in the statement. “We will work hard to secure justice for the victim, who allegedly was preyed on for more than a year.”

The case is not the first to involve accusations of wrongdoing by teachers and staff in the city’s public school system, the nation’s largest. A host of elite private schools, including the Emma Willard School in Troy, N.Y., and Choate Rosemary Hall, in Wallingford, Conn., have also recently confronted the issue of sexual abuse of students by faculty.

Reached by phone, relatives of Ms. Breton referred calls to Mr. Sapone.

“This is only Day 1 of the case,” Mr. Sapone said. He said Ms. Breton had grown up in New York and had been in a relationship with the same man, with whom she has two children, since she was 16. “Eleidy is a well-respected mother of two whose record is impeccable,” Mr. Sapone said. “We are in the middle of a sweeping investigation, the fruits of which will be revealed at the appropriate time.”

He declined to address accusations that Ms. Breton had tampered with evidence.

Ms. Breton was arrested last month, and was released on bail within a few days, Mr. Sapone said. She remains free.

On Friday, she was arraigned on a 12-count indictment including two counts of predatory sexual assault against a child, first and second-degree course of sexual conduct against a child, first-, second- and third-degree rape and tampering with physical evidence. She is scheduled to be back in court on Sept. 25 and faces 10 years to life in prison if convicted of the most serious charge, Ms. Clark’s office said.