He was described as popular with students and staff, many of whom have been left “deeply impacted” by his death.
“We will continue to support students and staff in the coming days and weeks as the wellbeing of our college community is paramount.”
Leo Hope died following a “sudden illness while travelling overseas”.
The school extended its condolences to Leo’s family and friends.
A candle-lit evening vigil was held in St Heliers on Monday to remember the teen.
Leo’s death was also mourned by the Marist Water Polo Club, where he was a member of the under-16 squad.
“A member of Marist since the U12 age group and currently part of our U16 squad, Leo grew up within our club,” the club said on Facebook.
“Along the way, he built lasting friendships with teammates, coaches and families, and was a valued and much-loved member of the Marist community.
“Leo will be remembered not only as a dedicated water polo player, but also as a valued friend and teammate whose kindness, spirit and presence enriched our club community.”
The club sent its “thoughts and deepest condolences” to Leo’s parents, Katie and Pete, family and friends.
“Leo will always be a part of the Marist Water Polo family.”