The alleged act happened in June last year and man was suspended by the school before resigning the following month.
Meanwhile, police have indicated they will withdraw a second charge of committing an indecent act laid over the alleged incident.
The NZ Teachers Council has confirmed the man has signed a voluntary undertaking not to teach, but has been suspended anyway.
"We know about the charges and our disciplinary investigation will be completed, a tribunal hearing conducted and a decision handed down after the criminal processes are completed," a council spokesman has said.
"In criminal charges of this kind we wait for the criminal process to run its course."