The Denver Post reported that the coroner’s office confirmed Jamel Myles died by suicide on Thursday.
Denver Public Schools spokesman Will Jones said Jamel was a fourth-grader at Joe Shoemaker Elementary School.
The boy’s mother, Leia Pierce, said: “My child died because of bullying. My baby killed himself.”
Ms Pierce told the newspaper that her son came out as gay this summer and began wearing fake fingernails on August 20, the first day at school.
She said she found Jamel’s body on Thursday and made an unsuccessful attempt to revive her son.
School district grief counsellors have met pupils, teachers and school staff.