During his professional training at UCLA, he served as Clinic Supervisor, Research Psychologist, Lecturer, and Interim Director of the Young Autism Project. He was extensively involved in many of the Young Autism Project research investigations, contributed to The Me Book, and is co-author of The Me Book Videotapes, a series of instructional tapes offering training for teaching autistic children. He is co-author of A Work in Progress, a manual on behavioral treatment of autism, It’s Time for School! Building Quality ABA Educational Programs For Students With Autism Spectrum Disorders, and Sense And Nonsense In The Behavioral Treatment of Autism: It Has To Be Said and Crafting Connections: Contemporary Applied Behavior Analysis for Enriching the Social Lives of Persons with Autism Spectrum Disorder.
Dr. Leaf has consulted nationally and internationally to families, school districts, day programs and residential treatment facilities. Dr. Leaf served as the Director of Straight Talk's Developmental Disabilities Services division for 15 years. This program provided residential and day treatment for adults with developmental disabilities. Dr. Leaf is also the Executive Director of Behavior Therapy and Learning Center, a mental health agency providing treatment, consultation and related services to parents, program staff and school personnel in the United States.