Any programme of principal induction must find ways to respond to the diversity of its participants, in terms of their backgrounds and learning needs. New Zealand's national principal induction programme uses a self assessment of each principal's capability in the leadership of teaching and learning as one of its main sources of information about the diverse learning needs of each cohort. This paper reports the results of a study of the validity of SALTAL (Self Assessment of Teaching and Learning), which is the tool used for this purpose. Factor analysis confirmed the theory of leadership upon which SALTAL was based, and scale analysis indicated the high reliability of the tool. Tests of its validity, using discriminant analysis, revealed that the tool correctly identified principals independently assessed as "highly challenged" or "high performing" but mis-classified those in the middle group. Overall, the results indicate the potential of SALTAL to assess the capabilities of a diverse group of principals and provide useful information for the principals themselves, their mentors and the programme team.