Four influential studies on school effectiveness reported by Brookover and Lezotte (1979), Edmonds and Frederiksen (1979), Phi Delta Kappa (1980), and Rutter and others (1979) are limited in their usefulness as recipes for creating effective schools by the following four issues: (1) The four studies differ in their definition of what "effectiveness" means. This variety of definitions should alert practitioners to the inadequacy of generalizing from these studies and the need to develop their own concept of effectiveness tailored to their particular situations. (2) The studies' lack of agreement on which characteristics most contribute to school effectiveness, and discrepancies between their conclusions and specific findings, should encourage practitioners to develop their own list of situation-tailored effectiveness characteristics. (3) The reliability of the studies' results is made questionable by the use of standardized, norm-referenced tests as indicators of academic achievement and by other aspects of the studies' research techniques and strategies. (4) Practitioners should be aware that the studies indicate correlations rather than causal relations, and thus refrain from using the studies as a recipe for creating effective schools. They should also heed the studies' emphasis on the importance of characteristics' interaction over any single characteristic. (JBM)