According to the Chino Valley Unified School District, the student was at school's aquatics center when he or she was in distress.
"At this time, District and school staff are working with the appropriate agencies to determine the student's condition, events leading up to first responders being dispatched, and how to best support students present during the medical emergency," said the district in a statement.
It's unclear if the student was in the pool or on the deck.
Other students were there at the time and have spoken with investigators. The incident remains under investigation.