Recent research stresses the key role of the contemporary principal to serve as an instructional leader who, in turn, promotes teacher growth and enhances learning outcomes. In contexts of both the developed and developing world, the role of the school principal or headteacher is changing in response to the increasing devolution of responsibility to school level and the variety of demands and pressures that this brings. The more the focus shifts to how effective each school is and how well its pupils are performing, the greater the need for pedagogic and organizational leadership.
http://www.worldbank.org/wbi/ictforeducation/html/schoolleaders.html