After defeating all Team Star bosses you'll have to fight against Clavell and Penny (aka Cassiopeia).
Team Star was formed by the school’s most rebellious students and is made up of several squads. Each squad is led by its own boss, each with their own base scattered across the Paldea region. These class-cutting delinquents cause trouble for all those around them, giving the academy’s students and teachers a hard time by disturbing the peace and using pushy recruitment tactics. March up to their bases and face off against the troublemaking Team Star!
Once you overcome the waves of Team Star Grunts, their boss will appear in a custom car called the Starmobile. It seems that during your Pokémon battles with these bosses, the Starmobile itself will get in your way. Take down each squad’s boss by defeating their party Pokémon and their Starmobiles!