Morgan, 70, of Auburn, was arrested after an investigation into allegations of ongoing abuse several years ago.
He is held at Placer County Jail in lieu of $1.5 million bail.
Morgan was a teacher at the school from 1998 to 2003 and a snowboard coach from 2003 to March 2011, said Eric Vereyken, human resources director for the Placer Union High School District.
Sheriff's officials are not releasing details, and it has not been disclosed when the alleged incidents took place or whether they involved students at the high school.
PHOTO CAPTION: Beldon Morgan