System-wide practices in schools should diminish the occurrence of children's problem behavior that is deleterious to academic achievement. The current study examined the relationship between variables that affect classroom behavior and observed behavior in schools with and without a theoretically based character education program. Observational data from 12 elementary schools compared control and treatment conditions on classroom disruption, and examined the influences of class size and percentage of students receiving a free or reduced price lunch (FRL). Results showed a weaker relationship between class size, FRL, and behavior problems within the character education schools than in control schools and that the character education program may have had a stronger influence in schools with a high percentage of students eligible for FRL. (Contains 5 tables.)