This study evaluated educationally relevant outcomes from a newly developed collaborative school–home intervention (Collaborative Life Skills Program [CLS]) for youth with attention and/or behavior problems. Participants included 17 girls and 40 boys in second through fifth grades (mean age = 8.1 years) from diverse ethnic backgrounds. CLS was implemented by 10 school-based mental health professionals at their schools and included 3 integrated components over 12 weeks: group behavioral parent training, classroom behavioral intervention, and a child social and independence skills group. Parent and teacher ratings of attention-deficit/hyperactivity disorder (ADHD) symptoms, organizational skills, and homework problems, and teacher-rated academic skills, report card grades, academic achievement, and classroom observations of student engagement were measured before and after treatment. Significant pre–post improvement was found for all measures, with large effect sizes for ADHD symptoms, organizational skills, and homework problems, and medium to large effects for teacher-rated academic skills, report card grades, academic achievement, and student engagement. Improvements in organizational skills mediated the relationship between improvement in ADHD symptoms and academic skills. Significant improvement in both ratings and objective measures (achievement testing, report cards, classroom observations) suggests that improvement exceeded what might be accounted for by expectancy or passage of time. Findings support the focus of CLS on both ADHD symptom reduction and organizational skill improvement and support the feasibility of a model which utilizes school-based mental health professionals as providers.