School boards are interested in school effectiveness and see a correlation between the quality of classroom teachers and school effectiveness. Superintendents, eager to please the school board, seek to show increased school effectiveness year after year. This necessitates dealing with areas which impact on student achievement with perhaps the most critical area being that of teacher effectiveness. The purpose of this study was to identify those factors which assisted marginal high school teachers in improving their classroom performance. Knowing to what or whom these teachers who showed improvement attributed this improvement may assist in modifying existing practices to increase the likelihood that such improvement will occur for a greater number of teachers. A survey was used to initially identify the teachers. A follow-up interview was conducted with fourteen teachers with the analysis of the transcribed interviews focusing on the following questions: 1. Did intervention/assistance efforts influence improvement? In what context were the intervention/ assistance efforts made? Who were the primary actors in the intervention/assistance efforts? What activities were influential in the intervention/assistance efforts? 2. Did external personal factors influence improvement? 3. Are there overarching characteristics, beliefs, and/or motives in the group of teachers who made substantial improvement in teaching performance? 4. What actor(s) provided to the teachers: (a) an awareness of the need for change and (b) support for change? 5. What were the teachers' perceived gains and losses in this improvement effort? Major findings revealed that teachers actively seek their peers' advice and desire to see one another in practice through peer observations. Sharing of ideas is important to teachers; yet, little opportunity exists within the school day for such sharing. Most staff development activities were seen as a waste of time and teachers resented activities which purported to "teach teachers how to teach." The most valuable activities to teachers were those things which they could take back and use in their classroom. As research has indicated, professional growth and development was primarily motivated by the teacher seeing results in the classroom and the resulting increase in teacher efficacy. / Ed. D.