The error was not spotted by any University of Glasgow staff, or by two internal exam boards and one external exam board.
Speaking at a press conference, Ms Scott said her son had been happy to secure a place at the university.
She added: “Ethan was a kind, caring young man who was very much loved.
“So it breaks my heart to now be aware of the mental anguish this university must have caused my son.
“The truth is, Ethan had successfully attained a 2:1 honours degree, despite the university repeatedly informing him he had been unsuccessful.”
Ms Scott said her son, who had “a smile that would light up the room”, reported difficulties with his mental health to the university.
But she said no support was offered.
Ms Scott added: “They failed him, not only academically, but also to support him.
“My son was failed from having a duty of care from the educational system, resulting in my family having been robbed from having Ethan in our lives.”