When did Troy and Gabriella break up and why?

Troy and Gabriella's breakup occurs in "High School Musical 2," specifically during the song "You Are the Music in Me." The tension arises from their differing priorities, as Troy becomes more focused on Basketball and his summer job, while Gabriella feels increasingly sidelined and disconnected from him. This strain in their relationship ultimately leads to their temporary separation. However, they reconcile later in the film, reaffirming their bond and commitment to each other.