The grim discovery was made at the Miguel Contreras Learning Complex, according to the Los Angeles School Police Department.
"We immediately notified law enforcement and are following Los Angeles Unified protocols," the agency said in a statement. "We are working closely with the Los Angeles School Police Department, the LAPD and the Coroner's Office who are working collaboratively on this matter. This investigation is ongoing, and additional information will be released as it becomes available."
The deceased person was identified only as "a student from the Miguel Contreras school community." The cause of death was not immediately released.
Access to the swimming pool was off limits until further notice, officials said, while the school remained open. Crisis counselors were available to any student or employee who may need additional support.
"On behalf of our entire school community, I want to offer my deepest condolences," an L.A. School Police Department spokesperson said in a statement. "At this time, we request that the privacy of those who have been impacted be respected during this difficult time. Please know that our entire school community offers our support."
In addition to resources available at the school, officials said, parents may also request support for their student by calling (213) 241-3840 from Monday to Friday from 8:00 a.m. to 4:30 p.m.