CONCLUSION
This chapter has reviewed the conceptual and practical interest in the definition of instructional leadership for theoretical and practical purposes. As described, the promise of a unique focus on instruction in the repertoire of educational leadership has yet to be met. Although more and more sophisticated techniques have been applied to the study of the ways in which school leadership affects student achievement, no consistently sustained identifiable line—or even lines—of research emerged focused on instructional leadership. Most of the research is conceived in apparent intellectual isolation and generates constructs about instructional leadership from scratch, that is, uninformed by any other scholarship. Such a failure in scholarship is variously termed "lack of generativity" or "compartmentalization" and, regardless of the moniker, points to a lack of sophistication in the field. These independent approaches include cross-sectional, large-scale studies with an overreliance on one type of data generation— perceptual data. Smaller-scale studies also fail to reference or replicate each other and have yet to produce any meta-ethnographies.