Applied Behavior Analysis, ABA, is a researched based education approach that is rooted in behaviorist learning theory. ABA involves systematically rewarding students for displaying desired behaviors in attempts to increase the frequency of the behaviors. For example, each time (or every few times) a student places a red object into the red sorting bin, the student will be allowed to play with a Koosh ball for 30 seconds. This practice of positive reinforcement helps to create a welcoming learning environment and is proven to produce results. 

For more information, please view this video from Autism Speaks:
Introduction to ABA