It is the beginning of the school year. At 13 years old, Ben discovers the effects of puberty on his classmates who have changed a lot. Especially Claire, who is now really pretty. Ben would like her to notice him, but he is hung up by his weight and even the school nurse worries about him. Despite his passion for cooking, Ben decides to go on a long and difficult diet. To face the bullying from Max and his gang, Ben can count on the support of his crazy family and his friends Claire, Eric and Sonia. Together, they start a band for the Christmas show, at the end of a year that will have made them all grow up, gain confidence in themselves, in life and in love.