Police have identified the body found behind Red Bluff High School on Thursday as that of 14-year-old Marysa Nichols.
They say they are classifying the case as a homicide.
The announcement was made by Red Bluff police investigators at a press conference Thursday night.
Nichols had gone missing Tuesday. She was last seen near the Red Bluff High School tennis courts by another student.
Dianne Whitmire, Marysa's mom, said she dropped her off at her independent school program just before 10 a.m. on Tuesday. The program is called Education Outreach Academy, and is located at Red Bluff High School.
Marysa reportedly told her mom she would walk home around 2:30 p.m., but never showed up.