At a time when schools face increasing pressures of accountability in both the economic and educational senses, there is a growing need for teachers to assume the role of evaluators of their own work. This study demonstrates that such a role can serve to fulfil both the specific demands of the teacher and school in assessing the worth of a program or innovation, and also the wider demands of the educational community, providing practical research data and results which may contribute to the improvement of teaching practice. The study investigates the use of hand-held calculators capable of graphics, calculus and symbolic manipulation as a means of enhancing the teaching of mathematics at the senior secondary level. The results indicate that such tools can bring about improvements in concept understanding, attitudes towards the subject and confidence in students' abilities in this regard.