According to the report on Adolescent Time Use by the Department of Health and Human Services, students who spend no time in extracurricular activities are:

57% more likely to have dropped out of school by the time they become seniors.
49% more likely to have use drugs.
37% more likely to have become teen parents.
35% more likely to have smoked cigarettes.
27% more likely to have been arrested than those who spend one to four hours per week in extracurricular activities.