C'est la rentrée des classes et pour renforcer le travail de groupe, le lycée met en place un nouveau programme : d'une part des cours de soutien donnés par les meilleurs élèves à ceux qui en ont besoin et de l'autre, l'organisation d'un tremplin musical. Cristobal, ses amis du foot, Luli et son frère Fernando se lancent dans le projet mais très vite chacun se retrouve confronté à certaines difficultés...

Football captain Cristóbal discovers that his neighbor and classmate, Mariana, has changed a lot over the summer. Meanwhile, Luli is still as vain as ever and overshadows her poor brother, Fernando. As a new year begins at High School Mexico (HSM, initially interpreted), the school has announced a "Battle of the Bands" contest hosted by Jesse & Joy. Working against the clock and with limited resources, Cristobal, Mariana, and a few of their peers unite as a band. In a desperate effort, Luli dares the impossible task of separating Cristobal from his friends. But only one band will be the winner; the one who understands that teamwork, personal development, and hard work will not only make them better artists but also better people.

Outro ano letivo começa e Cristóbal descobre que Mariana está diferente. Mas tudo muda quando o diretor da escola anuncia que haverá o "Desafio das Bandas", Cristóbal e Mariana terão que competir com a vaidosa Luli.