The Federal government mandates the use of evidence-based practice for interventions with students. Applied Behavior Analysis (ABA) is one of these evidence-based practices, but despite this, many school systems do not implement ABA as described in the literature, which leads to loss of fidelity and integrity with implementation, and often results in ineffective interventions in the classroom. The research question “What are the experiences of Board Certified Behavior Analysis (BCBAs) who use evidence-based practices in conjunction with staff in schools for interventions with American K-12 students using ABA?” was developed to ascertain, from a BCBA’s perspective, why ABA interventions are not implemented with fidelity in classroom settings. Participants were BCBAs in the United States who consult and collaborate with school staff to implement ABA services for children with autism spectrum disorders (ASD). Findings indicate that BCBAs are not given adequate time or resources to provide sufficient training in ABA, that principles of ABA are sometimes misused in training in such a manner that exacerbates myths of ABA, and that a general lack of support from school administrators exists, all of which lead to a loss of implementation fidelity. This lack of implementation fidelity in turn leads to decreased outcomes for students with ASD in schools when ABA is not implemented with fidelity.