To validate a proposed statistical index of instructional effectiveness, researchers identified 33 school characteristics related to instructional effectiveness and tested the relationship between these characteristics and the proposed index. The index includes two subject area indices, mathematics and reading, and is based on statistical projections from students' California Achievement Test scores, ethnicity, and eligibility for school lunch aid. A committee of 11 educators identified the 33 school characteristics, which included teacher activities, student activities, principals' characteristics, educational materials, school climate, and student and teacher mobility. Using 3 methods--classroom observation in 21 elementary schools, a questionnaire survey of 193 of the schools' teachers, and centralized data sources--researchers measured each school's scores on the 33 characteristics. They tested the characteristics' relationship to the proposed index by correlating each school's math and reading index score with its scores on the characteristics. The results indicate that the reading index has value as a measure of reading instruction effectiveness. A test of an initial causal model to explain the results reveals a poor fit and a need for further research on alternative models. A glossary describing the 33 characteristics and a copy of the teacher survey questionnaire are appended. (RW)