This paper presents a model describing three context variables hypothesized to affect measures of teacher efficacy. These variables include the nature of the student performance outcome (positive or negative), the ability of the students involved (high or low), and the scope of influence (single student or group of students). The results from studies investigating the influence of performance outcomes and student ability on teachers' perceptions of efficacy are summarized. The present study explored the extent of the effect of influence on the teachers' perceptions. It was discovered that teachers do distinguish in their perceptions of efficacy between results with a single student and those with a group of students. When poor performance was involved, teachers expressed less personal responsibility and efficacy for single students than for results from a group of students. A four-page list of references is included. (Author/CB)