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: During "Now or Never", Troy passes the ball to Chad who is standing on the left side (looking to the cheerleaders) of the white line drawn on the floor, but when he catches the ball he is on the other side. (00:04:30)
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: 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: 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: Just as Gabriella and Troy walk into Gabriella's backyard, they put their belongings down on the table, with an Adirondack chair beside it and the second Adirondack farther away from the table, mostly out of frame. Next shot, when they sit on the hammock, that second Adirondack which was out of frame has moved forward, so the end of its arm rest is level with the table's corner. When Mrs. Montez comes out it's back to the way it was in the first shot. (00:37:20)
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 and Gabriella are rehearsing "Just Wanna Be With you," Jimmie is seen painting in the background. In the first shot, Jimmie is crouching and gradually stands up. In the next shot, Jimmie is crouching again. (00:50:45)
Continuity mistake: During rehearsal, just after Ryan cracks up at the sight of Chad in the clown suit, as Taylor pulls Chad away Gabrielle walks to the center of the 'balcony', with her back to Troy. Next shot, however, Gabrielle is back near the corner or the railing facing Troy, but next shot she's farther away again. (00:51:50)
Continuity mistake: During the rehearsal of "Just Wanna Be With You", Jimmie leaves the cup of paint and paintbrush beside the railing. Not only does the cup of paint move (note rail post and pickets) in following shots, but after Gabriella dabs paint on Troy, the paint cup just vanishes, as well as the paintbrush Gabriella dropped. (00:52:05)
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)
Deliberate mistake: Troy and Chad drive into Riley's Auto Salvage and park the truck beside the trailer office (which Riley steps out of), near a tow truck. During "Boys Are Back", just after the shot with the female silhouette and the line "Save the girl," in the next shot Chad and Troy run past the trailer office, but Troy's truck has vanished. No worries, because the truck is back beside the tow truck after the song. (00:56:50)
Deliberate 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.
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.
Other mistake: When Tiara hands Sharpay the bag with the latte you can see that there is nothing in the bag, especially at the end of the scene when Sharpay tosses the bag behind her back. It would have spilled if there really was a latte in there.
Visible crew/equipment: The reflector screen is reflected in Kelsi's eyeglasses, in many shots throughout the film.
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: 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.
