This study examines how the introduction of TeachTown:Basics, a computer-assisted intervention for students with autism spectrum disorder, influenced teachers' use of other evidence-based practices. In a randomized controlled trial that enrolled 73 teachers nested within 58 schools, we used three-level hierarchical linear models to evaluate changes in teachers' use of evidence-based practices across the school year for those who received TeachTown:Basics versus those assigned to control. Both groups received training and implementation support to deliver three well-established evidence-based practices for autism spectrum disorder. Qualitative interviews were conducted with 25 teachers who used TeachTown:Basics to better understand their experience. Compared with teachers in the control group, teachers in the TeachTown:Basics group reported significantly less growth over the 9-month period in their use of evidence-based practices that require one-to-one instruction (ps < 0.05), but no difference in their reported use of evidence-based practices that do not involve one-to-one instruction (p = 0.637). Qualitative interviews indicated that teachers viewed TeachTown:Basics as an effective substitute for one-to-one instruction because it was less burdensome, despite the lack of support for TeachTown:Basics' effectiveness. Before introducing new practices, education leaders should carefully consider both evidence of effectiveness and the potential impact on the use of other evidence-based practices.