TOWARD A MORE APPROPRIATE CONCEPTUALIZATION OF RESEARCH ON SCHOOL EFFECTS: A THREE-LEVEL HIERARCHICAL LINEAR MODEL11The research reported here has been supported by grants from the Spencer Foundation and the Benton Center for Curriculum and Instruction at the University of Chicago. The authors wish to acknowledge the gracious assistance of David Myers in making a small subset of his Sustaining Effects data files available to us for this analysis. The authors also wish to thank Michael Seltzer for his thoughtful comments on an earlier draft of this manuscript.