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: 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.
Continuity mistake: When Sharpay steps to the front of the line-up, in the close-up she walks to stage right (viewer's left) passing Taylor, whose right hand is up beside her face as she holds a pen. Next wideshot Taylor's hand is down, penless.
Continuity mistake: After they all agree to do the show, when Ms. Darbus shows up and Chad tosses her the basketball, it keeps changing from two drawstrings, to one, back to two that hang down Chad's hooded sweatshirt.
Continuity mistake: When Gabriella and Troy are up in the treehouse, the three flower hair barrettes on Gabriella's right side form a triangle. Depending on the angle of the shot, the 'triangle' of flowers are formed with one flower at the top and two lower, or two flowers at the top with one lower flower.
Continuity mistake: In the scene where Troy and Gabriella are sitting on the edge of the treehouse, Troy's hands on his leg continue to move up and down suddenly, between shots.
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: After Kelsi signs everyone up for the Spring musical, when they all stand at the piano complaining, the notepad on the piano changes position depending on the angle of the shot.
Continuity mistake: During the musical number "Just Wanna Be With You," Troy jumps onto the railing and hangs off of it with one hand when he sings the line "no matter where life takes us." The paint on the railing is obviously still wet, because Jimmie can be seen painting it. However, in all subsequent shots, there is no white paint on Troy's hand until he climbs over the railing later in the song.
Continuity mistake: At East High at night, when Troy is sitting on stage talking with Ms. Darbus his hands/fingers are clasped together in side shots, but when the shots face him he is fidgeting with his ring.
Continuity mistake: Throughout the film, the multiple bracelets that Gabriella wears change positions on her wrist, between shots, depending on the camera angles.
Continuity mistake: Just before "I Want It All" in the cafeteria, Sharpay pushes Ryan's lunch tray away, then pushes it again some more off to her left. When the shot faces Ryan, the tray is back near Sharpay, but when the next shot faces Sharpay the tray has moved even farther off to her left again. She does not touch the tray between these shots.
Continuity mistake: In the cafeteria, just before "I Want It All", when Tiara places the 'reserved' sign on Sharpay's tray, its items change position between shots.
Continuity mistake: When Kelsi and Ryan sing "Last Chance" in the shots facing Ryan the music sheets overlap, but in the shots facing Kelsi there are spaces between the three sheets.
Continuity mistake: As Jimmy and Donny stand on stage wearing only towels, the way Troy and Chad are holding the boys' clothing differs, depending on the camera angles.
Continuity mistake: At graduation, while they are dancing, when Chad drops the basketball from under his arm Troy picks it up, but in the next shot Troy is not holding the basketball he is dancing with Gabriella.
Continuity mistake: When Troy and Chad are in the junkyard, Troy gets his hands dirty. In the next shot his hands are now clean.
Answer: I think that they are just props. The owner of those jerseys has no relevence to the plot.. They might just be randomly picked names.