Can we motivate student behavior in a first grade classroom? Reward System vs. Conventional Teaching Discipline Plan

What effect does a reward system have on first grade student behavior? Is there any way to have students behave better than they are currently? There is plenty of research conducted on different types of distracting behavior as well as different types of systems and programs that try to influence behavior. Three first grade classes were selected, observed, and data were recorded on any disruptive or unwanted behavior for three consecutive weeks. Post the first three weeks, a reward system was implanted for each class. Each class was given the opportunity to earn a “free day” in physical education class by decreasing their disruptive behavior during class. Only two of the classes were able to earn their free day