The incident occurred at San Jose National High School in Tacloban city, with one of two alleged suspects now in police custody, the Inquirer daily reported.
Police said one of the suspects -- a child "in conflict with the law" and a resident of San Jose -- was apprehended shortly after the incident, while another suspect remains at large.
Authorities have yet to release the identities of the victims as investigators are still determining the circumstances surrounding the shooting, including the motive behind the attack.
The relationship between the victims and the suspects has also yet to be established.
Police have launched a manhunt to locate and arrest the second suspect.