The Twin Rivers School District said that the nude photo had been sent to cell phones of some students who forwarded it to more cell phones and posted to a Facebook group.
Hillsdale Elementary School principal Renee Scott-Femenella called the Twin Rivers Police Department over the incident, reports CBS Sacramento.
"That is my major concern, is that the school is not communicating with us, the parents." said an unidentified parent.
"This is becoming a very serious issue among juveniles, because parents are buying the kids smartphones," said criminal defense attorney Jennifer Mouzi.
"In an effort to teach students about Internet safety, the Hillsdale principal and a TRDPD officer have met with both sixth-grade classrooms to clearly let students know about the illegality of sending or posting inappropriate photos," said the Twin Rivers School District in a statement