VACAVILLE, Calif. -- A teacher's gender reassignment surgery has caught the attention of some parents who want to know why the school district didn't notify them ahead of time about the change.

A music teacher at Foxboro Elementary School, who was formerly a woman, returned to school as a man at the beginning of the school year.

The teacher, who was not identified by KCRA 3, is now being addressed as "Mister."

Some parents told Travis Unified School District that they feel like their rights to know were violated.

"All the information came straight from our kids and didn't come from the school board or the teachers ... this has all been second-hand information," parent Melissa Oiland said.

The district said it has to respect privacy and personal issues, and that it must preserve privacy rights of the teachers.

The school board said such disclosure would violate HIPAA privacy rules.

"I understand what parents are saying, but we have a right as an employer, we have a legal obligation as an employer to protect our employees," Superintendent Kate Wren Gavlak said.

Gavlak said the district consulted with lawyers and determined that legally, it could not disclose any information about the teacher's gender change.

"We will not be discussing personal matters with either the students, or the parents or the community at large ... because we cannot," Gavlak said.

Parent Angela Weinzinger, who has three children at the school, said she has since transferred her children out of the class.

"I wasn't given the opportunity to make a choice on what I wanted to do with the situation," Weinzinger said.

So far, 23 students from 15 different families have transferred their children out of the music class and into a physical education class.