The Sag Harbor School District identified the child as Cesar Albarracin Guncay.
The coroner's officer determined the Pierson Middle School student died from accidental drowning.
Superintendent Jeff Nichols said in a letter to parents the accident occurred during the annual class trip to the Poconos. About 74 students were on the trip.
"On behalf of the entire district, we extend our deepest condolences to Cesar's family and loved ones during this extraordinarily difficult time," Nichols said in the statement. "We ask our community to honor Cesar's memory and keep his family in our thoughts."
A large group was rafting Wednesday around 5 p.m. when the inflatable raft flipped over. There were five children onboard and four of them were rescued, according to the Pennsylvania Fish and Boat Commission.
They said the victim did not immediately resurface. He was later found by search and rescue teams and pronounced dead just before 7 p.m.
Drone video showed a raft overturned and pinned against a fallen tree in the river.
Nichols said school counselors will be available for students and staff.
"There are no words to adequately express the depth of this loss. Cesar was a cherished member of our school family, a child who mattered deeply to all who had the privilege of knowing him," Nichols said. "His absence will leave an irreplaceable space in our classrooms, our hallways and our lives."
A GoFundMe describes the 12-year-old as kind, handsome and an athletic 6th-grader, a friend to many and a beloved neighborhood kid.
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