The defense attorney for 31-year-old John Azabache said his client's former fiancee is on the prosecution's witness list.
Police in Ossining have charged Azabache, of Port Chester, with two counts of third-degree rape. Azabache, a math teacher at Ossining High School, had sex with the girl twice since March 1, police alleged.
Defense lawyer Tony Castro said Azabache pleaded not guilty and posted $50,000 bail. He said the charge does not allege forcible compulsion. By law, a 16-year-old is not capable of consenting to sex with an adult, he said.
Police said the sexual contact did not happen on school property or during school hours.
Castro said Azabache's wedding, originally scheduled for Friday, was canceled some time ago. He would not say if the cancellation was related to the charges.
"The wedding is not a matter of interest to me as his defense lawyer," Castro said.
Azabache is due back in court on July 23.
Ossining School District Superintendent Raymond Sanchez said officials were "disturbed and appalled" by the charges. Counseling is being offered to students next week.
Sanchez said Azabache was hired in 2008 and had no prior criminal record. He has been "administratively reassigned" and barred from school grounds, the superintendent said.