VIDEO: Katy Perry Performs 'Roar' at Contest-Winning High School

Katy Perry celebrated her 29th birthday today by giving a private concert at the Colorado high school whose spirited video featuring her pop anthem "Roar" won the "'Good Morning America's 'Roar' With Katy Perry Contest." Check out the performance below!

Perry chose the winning video, which featured over 2,000 students and staff at Lakewood High School in Lakewood, Colo., lip-syncing to Perry's lyrics group by group. Everyone from student athletes to cheerleaders to members of the pep band showed off their school spirit.

"It was thousands of kids coming together to 'Roar' and that's what this competition means to me," Perry told "GMA."

Perry, who just released her new album, "Prism," told the crowd, "I'm 29. I feel great. I still feel like I'm 13 sometimes. Obviously you can tell by my music and my spirit. I'm so excited about this record and I just love all the participation and the unification ...of all of you guys coming together and roaring."

Perry also sang her new single, "Walking on Air," and her classic, "Firework."

VIDEO: Katy Perry Performs 'Roar' at Contest-Winning High School