An elementary school teacher who had a sex-change operation has sparked ire among some parents who are demanding to know why no one told them in advance about the gender switch.

A music teacher at Foxboro Elementary School in Vacaville, Calif., was previously a woman, according to KCRA.com. But she returned as a man at the beginning of the new school year in September.

Some parents were outraged, saying they felt it was their right to know.

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

But Travis Unified School District says it was legally obligated to protect the unidentified transgender teacher's privacy under the HIPAA law.

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

Click here for more on this story from KCRA.com.