First Step to Success (First Step; Walker et al., 1997, 1998) is a secondary-level intervention for students with behavior problems in early elementary school. The purposes of this study were to assess whether effects in student behavior and academics at posttest shown in a recent efficacy trial (Walker et al., 2009) were maintained at follow-up and to examine the relationship of implementation fidelity to outcomes. The findings showed that although First Step's initial impact was significant and positive across all behavior and some academic measures, gains eroded 1 year after the intervention was withdrawn. Results are discussed in the context of students' experience of yearly change in classroom environments, teachers' variable behavioral expectations and perceptions, and the need for intervention maintenance plans to support sustainment of treatment effects.