Continuity mistake: At Riley's Garage, when Troy and Chad are about to rummage through the junk looking for the radiator cap, Troy raises his arms and his boxers are light grey, but next shot when he lifts the truck's hood his boxers are black. It's also noteworthy to mention that during "Boys Are Back," young Troy is wearing patterned boxers, though all other clothing is identical. (00:53:45)
Continuity mistake: When Tiara is at Sharpay's locker, she holds out the pink shopping bag with her left hand, but next close-up it's in Tiara's right hand.
Continuity mistake: When Coach Bolton confronts Troy about Juliard, and then when Troy is at East High at his locker changing into his Wildcat jersey, he is wearing dark boxers. When Troy is on the stairs singing "Scream", before reaching the cafeteria, his boxers are light blue.
Continuity mistake: When Gabriella holds up the toy Robot Rob to Troy, the robot's left arm sticks out in one shot, but is down to its side in the next.
Continuity mistake: When Taylor reads Gabriella's acceptance letter from Stanford University, the envelope behind the letter is positioned in Taylor's left hand vertically, but in the closeup the envelope is horizontal between both of her hands, and then it's back to vertical. This mistake occurs between shots. (00:47:40)
Continuity mistake: When Troy is focused on the game at the beginning, his hair is soaking wet due to sweat perhaps, but when he is in the locker room during half time, his hair is dry. (00:01:55 - 00:02:45)
Suggested correction: He had a towel around his neck meaning he dried off his hair.
Continuity mistake: At Riley's Garage, after Troy finds the radiator cap he lifts the truck's hood and tosses the red t-shirt onto the engine. Once he removes the duct tape and places the cap on, back to the side shot the t-shirt has changed position.
Continuity mistake: At the graduation, during the song High School Musical the staff members are standing on the stage while clapping along, but in the next shot the staff members are no longer on the stage, then they are back on stage.
Continuity mistake: When Troy surprises Gabriella from behind he pulls her into the treehouse, and as they stand at the center holding hands, behind Gabriella is the brass bell (which is at the doorway they sat in front of earlier) and behind Troy are two model airplanes. In the next two shots as the ceiling opens, though the couple have not moved, now the airplanes are behind Gabriella and the brass bell is behind Troy, but they revert back to their original positions in the final shot inside the treehouse. (00:12:05)
Continuity mistake: When Sharpay appears at Troy's locker to let it slip about Gabriella's 'Freshman Honors Program', Troy's notebook changes position. Such as, the front of Troy's notebook (with the Wildcat sticker) faces out, but in a close-up the back (cardboard color) faces out.
Continuity mistake: When Gabriella joins Troy on the roof, she places her bag on the step before she picks Troy's tux. The bag's position changes throughout this scene.
Continuity mistake: After their musical number during the show, when Troy hands Gabrielle the bouquet of roses, the white ribbon is either higher up in the close-ups or lower down in the wideshots.
Continuity mistake: On the treehouse, when Troy helps Gabriella up during their song, "Chad's" red cape, which is draped to the floor, and Robo Rob are visible behind them on the windowsill. In the next shot as Troy removes his sweatshirt, only a bit of the cape is draped over and the toy has moved farther away from the window's frame. When they turn the corner, we can see that more of the cape is draped on the inside of the treehouse again. (00:11:40)
Continuity mistake: In the cafeteria, when Taylor agrees to be Chad's date the blonde wavy haired girl is sitting behind Chad, but next shot she's excitedly standing, then back to sitting when it cuts away.
Continuity mistake: When Gabriella and Troy walk into her backyard, Troy drops his book down on the table, with its spine facing the gate, but next shot the book has rotated about 90°.
Continuity mistake: Chad and Troy bring Zeke's dessert to Gabriella and Taylor, with orders to polish off the evidence, when the girls are working on the yearbook. The photos and papers on their desks change between shots.
Continuity mistake: After Kelsi signs everyone up, and they stand around the piano complaining, in the shots facing Gabriella she stands directly in front of the notepad, with her hands on the piano to the left and right of the notepad. In the shots facing Kelsi, Gabriella stands to the side of the notepad. This occurs between shots, particularly noticeable when Troy tells them he's in. (00:19:05)
Continuity mistake: When Troy and Gabriella are sitting in the treehouse, depending on the angle of the shot, Gabriella's upper body is turned more towards Troy, or is parallel to him.
Continuity mistake: In the musical number at graduation, Ryan's shirt un-tucks and re-tucks several times during the dancing.
Continuity mistake: The balcony railings are being painted during rehearsals with white paint and the cast get paint on their hands. However, in the final show the railings are wooden, stained with a colour.