In Chapter 2, I alluded to the fact that leadership was purposely omitted from my model of factors associated with student achievement. This is not because leadership is unimportant. On the contrary, leadership could be considered the single most important aspect of effective school reform. It is frequently mentioned in the early research on school effectiveness (Brookover et al., 1978, 1979; Edmonds, 1979a, 1979b, 1979c, 1981a, 1981b; Purkey & Smith, 1982, 1983; Rutter et al., 1979) and continues to be a staple in the research (Scheerens & Bosker, 1997; Teddlie & Reynolds, 2000).

The strongest reason for separating leadership from the model of factors is that it influences virtually every aspect of the model presented in this book. Leadership is a necessary condition for effective reform relative to the school-level, the teacher-level, and the student-level factors. To illustrate, research indicates that leadership has a strong relationship with (among others)

• the extent to which a school has a clear mission and goals (Bamburg & Andrews, 1990; Duke, 1982),
• the overall climate of the school and the climate in individual classrooms (Griffith, 2000; Villani, 1996; Brookover et al., 1978, 1979; Brookover & Lezotte, 1979),
• the attitudes of teachers (Brookover & Lezotte, 1979; Oakes, 1989; Purkey & Smith, 1983; Rutter et al., 1979),
• the classroom practices of teachers (Brookover et al., 1978; Brookover & Lezotte, 1979; McDill, Rigsby, & Myers, 1969; Miller & Sayre, 1986),
• the organization of curriculum and instruction (Bossert et al., 1982; Cohen & Miller, 1980; Eberts & Stone, 1988; Glasman & Binianimou, 1981; Oakes, 1989), and
• students' opportunity to learn (Duke & Canady, 1991; Dwyer, 1986; Murphy & Hallinger, 1989).