In 2018, the national EnCLASS survey polled 20,577 middle and high school students aged 11 to 18 about their well-being, health behaviors, and use of psychoactive substances. The initial results of this survey, coordinated in France by Emmanuelle Godeau, a professor and researcher at EHESP, and Stanislas Spilka, head of statistical surveys at OFDT, and published in 2019, focused on data regarding alcohol, tobacco, and cannabis use in middle and high schools. Nine thematic fact sheets developed in partnership with the French Ministry of National Education, Inserm, and Santé publique France complement the findings on substance use by revealing middle school students’ behaviors and perceptions regarding bullying, school experiences, diet, physical and sports activities, disability, sleep, sexuality, mental health, and prevention initiatives implemented in middle schools. This fact sheet focuses on mental health and well-being. The majority of middle school students perceive themselves as being in good health and have a generally positive view of their lives (nearly 9 out of 10 students); ? Approximately one-third of 8th and 9th graders show a moderate or high risk of depression, and 4 out of 10 students report recurring somatic and/or psychological complaints; ? Overall, girls have poorer mental health than boys (poorer self-reported health, less positive perception of their lives, higher prevalence of somatic and/or psychological complaints and depressive symptoms); ? Girls’ mental health deteriorates between 6th and 9th grade (perceived health, life satisfaction, recurring complaints, and risk of depression); ? More than one in ten high school students report having attempted suicide at some point in their lives, and 2.5% report having made a suicide attempt that resulted in hospitalization; ? Over the 2014–2018 period, a greater number of middle school students have a positive perception of their lives; the prevalence of recurrent somatic and/or psychological complaints remained stable despite an increase in nervousness and irritability; ? Compared to their European peers, French middle school students aged 11, 13, and 15 report more recurrent somatic and/or psychological complaints.