If you are considering a career as a therapist specialized in Applied Behavioral Analysis, I would recommend gaining admission into a Masters program that has an internship requirement and for your internship year work in a facility that trains you in ABA.
Alternatively, volunteer somewhere shadowing an ABA therapist during your graduate program if there is no practicum or internship year requirement. Simply learning about ABA in classes and writing papers about it will not be as useful as completing a formal training internship in the area or shadowing someone as a volunteer. Make sure you have the capability of being a licensed professional after the completion of the program, as your license will help you find better jobs that pay well. Unlicensed professionals have difficulties finding employment in the field of psychology, especially if you will be working with special needs children.
Hope that helps.