As for Sharpay and Ryan, they talk about how to separate ...... two people with the same father and mother, even if the university is not the same, but also have to go back to the same home it. It's just that the plot needs an antagonist to move the plot forward, and Sharpay is a good girl after all.
As for Casey and Ryan's romance (?). I think it was entirely to add a perfect ending to their high school graduation. Isn't it complete that everyone has their own emotional affiliation and that the lineup is directly reflected in that dance drama they rehearsed where everyone has a partner.
It's only natural that graduation season should have a happy ending for everyone, but graduation is graduation, and no one knows what's going to happen in the future. As long as the memories of East High School remain in their hearts, those happy memories, that's the perfect ending~