This study was conducted in order to determine the impact of a 3-year, theory based, inservice training program on teaching effectiveness for classroom teachers. Feedback on observed teaching effectiveness competencies was provided for each teacher in the study sample, along with a profile of student learning styles and data on student perceptions of the classroom environment. This information provided the basis for determining each teacher's needs, upon which teaching strategies were planned. Participants included vocational high school teachers drawn from seven schools. The sample was divided into three groups: (1) two schools designated as full treatment experimental group X; (2) three schools identified as medium treatment control group A; and (3) two schools designated as a minimum treatment control group B. Teachers were told they would receive information about their teaching that would help improve their effectiveness. Results suggest that inservice programs conducted over a 3-year period had a positive outcome in increasing effectiveness for those teachers in the experimental group. The theoretical base was understood and applied by teachers, and their teaching effectiveness scores showed marked improvement as measured by three different instruments. (LL)