Follow the summer of Billie's 16th birthday, a lifeguard at the water park, with her two best friends, Rosine and Juliette, as well as her perfect big sister, Annette. Billie's summer is quickly turned upside down when she falls in love with a charming cycling champion.

When Maria thinks she's at the bottom of the barrel, she discovers that this barrel has a double bottom: no job, no money, no worthy accomplishment and now a dying mother begging her to do something with her life. before his death! She has no other choice but to get back in hand and find a career ... But what can she do with a 7-year-old BAC in communication and no work experience? Believe it or not, she can become a substitute in a high school! Thus, Maria, 30, as responsible and stable as a 14-year-old teenager, returns to high school in the role of the one to whom she threw pieces of erasers: the replacement. Too jaded teachers, rebellious teenagers, intimidated or not sufficiently denounced, she will be confronted with the reality of teachers and young people today and, who knows, may discover a vocation.