A study was conducted (1) to determine whether or not length of school experience affects teachers' ability to deal with difficult classroom situations in ways which are constructive rather than punitive and (2) to analyze the effects of an experimental course designed to help them translate psychological principles into appropriate response behavior. A panel of five judges categorized 1500 "difficult" classroom situations gathered from teachers, and built the 30-item Classroom Situation Questionnaire which was administered to 173 teachers with varying lengths of experience. The judges classified their responses to the situations in terms of the diminishing-interruptive vs. the non-diminishing, non-interruptive dimension of classroom behavior (i.e., the extent to which teaching behavior was interruptive of the learning process because it diminished the self-concept of students, class, or teacher). Analyses of variances did reveal response differences, with the most productive teacher behaviors occurring at the third and between the sixth and tenth years of service. The experimental course was given to 156 teachers; 30 not enrolled were a control group. Analyses of variance of repeated measures resulted in F ratios indicative of significant differential effects between the two groups beyond the .01 level, with the experimental group changing positively, the control group negatively. (JS)