A child's brain exhibits its highest levels of plasticity during the first few years of life. 

Specific play-based therapies, such as the Early Start Denver Model (ESDM), are specifically tailored for toddlers between 12 and 48 months of age. However, ABA is not exclusively for very young children. 

Extensive research documents the clinically important impact and effectiveness of ABA for older children, adolescents, and young adults between the ages of 5 and 21, helping them build essential life and social skills.