Brandon McInerney, 17, was on trial for the 2008 shooting death of junior-high classmate Lawrence King. He was tried as an adult.
The jury failed to reach a verdict and the judge declared a mistrial Thursday.
The Ventura County District Attorney's Office says it will seek to have the case reset for trial.
In the meantime, Jim Ellison, the chief assistant district attorney, will be interviewing jurors to see how the original charges against McInerney should be modified.
McInerney was being tried for murder with a hate-crime enhancement in the shooting death of classmate Lawrence King in 2008.
McInerney, then 14, shot King twice in the back of the head in a classroom at E.O. Green Junior High School.
The prosecution alleged McInerney had planned to shoot King over unwanted sexual advances, and said that McInerney had white-supremacist leanings.
The defense contended McInerney had a violent upbringing in a rough household and that he snapped when King, who was gay, made repeated comments to McInerney.
McInerney, now 17, was tried as an adult.
The nine-woman, three-man jury panel said the last vote resulted in seven in favor of voluntary manslaughter and five for first- or second-degree murder.
The trial was moved to Los Angeles County due to media coverage.
The jury began deliberations last Friday.