Continuity mistake: When Sharpay starts singing "Want It All" there is a girl behind her wearing jeans and a red shirt sitting with her legs crossed. When the Shot changes to Ryan, the girl is crossing her legs again and then they are crossed when it goes back to Sharpay.
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: 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 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 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)
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)
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)