The homeless student was named valedictorian at First Coast High School in Florida after he ended up with a 4.65 GPA despite not having a home to study in.
Furlong lost his mother to leukemia when he was 6 and has spent time living in shelters and the homes of friends and relatives.
The 18-year-old is set to graduate in June and he hopes to study civil engineering at Florida State University.
"I wrote him a letter of recommendation, and I said he was the hardest working, most-motivated student I have ever had," Jennifer Stover, his calculus teacher, told First Coast News.
Furlong plans to discuss his family's plight in his valedictorian address.
"At some point I wanted to quit. It was horrible." Furlong said. "A kid should not have to go through that. I know that I have everything to lose. So I just push myself. School is all I have, family is all I have. I am doing it all for me and what I have been through. I am doing it for my mom."