The use of both empirically supported and unsupported practices by teachers is common with autistic students. In this study, strategies were used to reduce use of unsupported practices. First, specially-designed information sheets were shared with teachers about the evidence-base of two practices used in schools: one unsupported (sensory integration therapy [SIT]) and one supported (antecedent-based interventions [ABI]). A professional development program was then implemented to improve knowledge and use of ABI. The information sheets significantly reduced teacher support for SIT, however this was not maintained following professional development. Support for ABI remained unchanged across phases. The need for ongoing teacher professional development in replacing use of unsupported practices with more evidence-based approaches is discussed.