Joanna Ramos, 10, died at a hospital in February just hours after fighting with another girl.
Friday police said they have handed their investigation over to the D.A.'s office.
Prosecutors now plan to determine whether the victim's opponent should face charges.
Ramos was a fifth-grader at Willard Elementary School in Long Beach. She died from blunt force trauma she suffered during a planned fight, which friends said was over a boy.