The fire at ‘Eua High School broke out in the early hours of Thursday morning.
Kaniva News reports a close family member of the deceased alleged the victim is thought to have been trapped in his house before he could be able to escape the fire.
He was rushed to hospital where he died, she said.
It is understood the victim went by the name of Kalisolaite ‘Eti on Facebook.
Viliami Tu’ihalamaka from Tonga Fire and Emergency Service in Tongatapu said he had received report from ‘Eua a man was injured in a house fire at the school and was taken to hospital.