For motivating students youths
and children

Motivation is a theoretical construct used to explain behavior. It represents the reasons for people's actions, desires, and needs. Motivation can also be defined as one's direction to behavior, or what causes a person to want to repeat a behavior and vice versa. A motive is what prompts the person to act in a certain way, or at least develop an inclination for specific behavior. According to Maehr and Meyer, "Motivation is a word that is part of the popular culture as few other psychological concepts are."

For more reference :
http://everydaypowerblog2014/11/06/10-best-motivational-books-for-personal-development/