Revealing mistake: When Troy says "I'll sing with her," Ms. Darbus turns around "in response" to his voice before he even says anything.
Revealing mistake: In the final scene "We're All In This Together", when Ryan is getting ready to jump off of the bleachers and be caught by his classmates, you can see Troy motion for Gabriella to move forward into the correct position for the shot.
Revealing mistake: In the cafeteria scene, when Gabriella slips in the spilled milk, her tray is not only shot up, but tilted as well. However, after the camera cuts back to Gabriella, there is a cup of "sauce" yet it doesn't slide or tip off the tray.
Revealing mistake: When Troy and Gabriella are singing "What I've Been Looking For", near the beginning of the chorus, Zac Efron looks at the camera, then looks away. He does this again near the end of the song.
Answer: I'm not positive, but that is what I've always assumed.