'High School Musical' director confirms Zac Efron did sing in the first film 

Kenny Ortega is clearing up whether High School Musical star Zac Efron really sang in the franchise's first film, and his answer might surprise you. 

"[He was only] partially [dubbed]," the director explained to ET. "He sang in the first show. The songs were written before Zac got the role. So, although he could sing and he had a lovely voice, it wasn't the voice that the songs were written for. So he sang everything, and then we dubbed parts of it so that it had greater vocal strength. But [for] the second movie and the third movie, everything was written for him. And that's important, that people know that Zac Efron did sing." 

His vocals were dubbed with Drew Seeley's. 

While watching the performance of "We're All in This Together," he commented, "They were just so lost in those characters," continuing to add, "I knew something special was going on here because of Dirty Dancing. There was something electric that was happening in the room during 'We're All in This Together.' They were so into that song, and when I called cut, the place erupted. It was like human fireworks."