Although teacher effectiveness research has to date been primarily concerned with class level statistics, valuable information regarding a teacher's proficiency can be gleaned from the analysis of within class data. The relationships between teacher behavior and student achievement vary at the differing levels of analysis. Nine variable patterns of teacher behavior yield alternative response on more than three categorical levels: students within reading groups; reading groups within classes; and classes. Cross-group study of these levels, when compared with in-group study, provides information concerning not only the competency of the individual teacher but also the relativity of the individual student's achievement level to that student's social group. A synthesis of the two types of statistical analysis is necessary to obtain a comprehensive view of the dynamism between student-teacher interaction and student achievement. (LH)