This study investigated the efficacy of counseling and psychotherapy interventions for youth in schools. Data were examined for 107 studies that included 132 treatment interventions. Overall efficacy was d = 0.45 and was significantly different from zero. Interventions for adolescents outperformed those of children, treatment groups that were predominately female or male did better than mixed-gender groups, and licensed professional therapists outperformed paraprofessionals, who outperformed graduate students. Implications for supporting the mental health needs of youth in schools are discussed. (Contains 4 tables.)