When Troy and Gabriella are about to sing 'Breaking Free' on stage for the final doubles audition, approx 1 hour 20 mins into the film.

The piano starts playing the intro and Gabriella is about to start singing but then gets nervous and is motionless, piano stops and Troy tells her its ok, then they try the song again but its really Troy who has the first line 'We’re soarin’, flyin’', meaning that first time round he should have started first.