John Benstock, 47, was arraigned Wednesday on a 31-count indictment. His attorney said he was expected to post $250,000 bail.
Nassau County District Attorney Kathleen Rice said the allegations date back 11 years. Benstock was arrested in May on a misdemeanor charge of child endangerment involving one child. A grand jury later indicted him on charges involving 13 other children.
The Locust Valley teacher has been suspended until the case is resolved.
Attorney Chad Seigel suggested the victims were not properly questioned and cautioned against a rush to judgment. He added that Benstock has supporters in the community and among colleagues.
Benstock, who lives in Bayville, is charged with 15 felony counts of course of sexual contact against a child, two felony counts of first-degree sexual abuse and 14 misdemeanor counts of endangering the welfare of a child.
He faces up to seven years in prison for each felony count.
Rice said that as early as 2000, Benstock engaged in inappropriate contact with students in orchestra classes at two Locust Valley elementary schools and during private lessons in the students' homes. All of the children were under 11 years old when the charged events occurred.
"Parents trusted this defendant to teach their children music, but he abused these innocent kids for his own sick pleasure," Rice said. "My office will aggressively prosecute this case to make sure this defendant never puts another child at risk again."
Anyone with information regarding additional victims is encouraged to contact the Nassau County Police Department Special Victims Squad at (516) 573-4022.