Other mistake: At graduation, after Troy is handed the diploma, in the overhead shot the graduates on the left and right stand-up from their seats, then turn and walk towards each other. All their seats simply disappear between shots. Obviously done deliberately for the dance sequence, but a mistake nonetheless.
Add timeSuper Grover
Other mistake: In the scene where Ryan joins Kelsi for early-morning rehearsal, Ryan sits at the piano and starts playing "Just Wanna Be With You." However, the sheet music only shows the melody, not the actual music, and this is the first time Ryan has seen the song, so he has no possible way of knowing how to play it.