This review paper begins by asking what makes few schools outstanding. What makes them successful? What have we learned from last two decades of studying School Effectiveness (SE)? To answer those questions, this paper attempts to identify the patterns and trends of Studying School effectiveness from western perspective. The main purpose of this review study was to understand and fix the criteria of assessing SE. A brief literature review was carried out to bring those factors that contribute SE. The focus is on the substantive findings that emerged from the review. Literature gives an insight that educationists have given more importance to enrolment, retention, and dropout rates, whereas many have viewed SE in terms of classroom pedagogy or teaching and learning, the content aspect, etc. The large section of effectiveness studies have focused exclusively on students' cognitive outcomes in the areas such as reading, mathematics or public examination results. However, there is less evidence about the studies on school processes indicators that are important in determining the schools' success. The results from reviewed literature reveals that many SE factors, three broad key process indicators have found to be the most frequent ones, i.e. effective leadership of school heads, positive school culture and environment of teaching and learning. The critical perspective of previous literature are useful in understanding how this set of key variables as a whole defines the quality of schools at all levels. Finally, it provides few recommendations for policy development to bring about improvement.