Continuity mistake: At Lava Springs, when Fulton hands Sharpay the marker (to autograph the talent show fliers) it is capless, but in the close-up as she signs her initials the pink cap is on the marker, but then it vanishes again. (00:11:35)
Continuity mistake: When Chad and Troy show up to caddy for the Evans family, the positions of Ryan and his mother, as well as the golf club bags, change depending on camera angle. The shadows they all cast also repeatedly change.
Continuity mistake: In the L.S. kitchen, when Fulton gives Troy the suit and tie, the hanger's metal swivel hook changes direction between the three shots.
Continuity mistake: During Sharpay's version of "You Are the Music In Me" after she tosses her red jacket atop the piano it moves from front to side, again and again, during the song. (01:12:25)
Continuity mistake: When Sharpay, Ryan and the three Sharpettes sit on their chaise lounges before "Fabulous" there are three large umbrellas behind them and a table with Sharpay's imported ice tea on it. It all disappears during the song; additionally, their large brightly colored bags and magazines move as well. (00:13:40)
Continuity mistake: In Ms. Darbus's classroom, when "school's out" is written on the board, the handwriting differs from shot to shot. (00:02:10)
Continuity mistake: During 'Work It Out', when Troy is finished tapping on the gold cookie tray Gabriella places it on the bottom shelf of the large prep cart. That tray repeatedly goes from right-side up to upside-down in the following shots. (00:23:15)
Continuity mistake: During 'Work It Out', Gabriella grabs the large gold cookie tray from the side rolling cart and turns with it (couple of shots after she clinks the glasses), but next shot she grabs that gold tray from the bottom shelf of the large prep cart. What's particularly funny about that second shot is the fact that the gold tray was never on that prep cart's bottom shelf until later on in the scene, after Troy taps on it. (00:23:10)
Continuity mistake: During I don't dance after the dance with the bats and then Chad's group comes in they throw or do something to the bats the next shot they are gone and then you don't see the bats for some time and then after some time they come back BUT there are not enough bats for the team.
Continuity mistake: In the very beginning of "Go My Own Way," Gabriella starts to turn away from Troy twice; once in a shot from over Troy's shoulder and again when it is a side shot of the two of them.
Continuity mistake: During the final dance scene, "All For One," the sky in the background constantly changes from blue and cloudless to overcast.
Continuity mistake: During "Everyday" Troy's microphone keeps switching hands.
Continuity mistake: During "Work this Out" you see a girl pass by Taylor during the line "I don't remember you saying the boss is such a creep". The next shot you see the same girl move by closer to Taylor.
Continuity mistake: Troy's hair constantly changes throughout the movie.
Continuity mistake: During "What Time Is It" Jason is laying his head on his desk. His arms are change between shots.
Answer: It's a Musical. Instruments that aren't shown are always playing like this in these types of movies.