The effective operation of a school unit relies on various factors, the most critical of which is leadership, as it this which shapes the working environment through which the school succeeds or fails. Indeed, an effective leader can inspire vision and promote educational policy in the interests of the school and other stakeholders. This leadership role in schools is undertaken by head teachers, who are called to act as supervisors of the school’s human resources in parallel with their purely administrative work. In order for school leaders to achieve these outcomes, however, they must be adequately trained so as to be competent in undertaking the arduous task of leading a school unit. Consequently, in order for school leaders to carry out their daunting tasks successfully—in other words, achieve the best possible results with the fewest sacrifices and least effort—they must possess certain knowledge and aptitudes. For this reason, the staffing of the school units in any country (and hence in Greece) with capable school leaders should be the top priority of the State, while measures should be taken to ensure that the processes for selecting school leaders and for their professional development remain objective and systematic, if the country intends to implement an educational policy efficiently and effectively. Taking into account that the school leader is not born but becomes, and that school leaders are central to the administration of a country’s educational system, it is vital that a system of selection and development of schools’ head teachers be institutionalized.