Sorting out the good from the bad has long been a human activity, and one that is essential to society itself. Although institutions have often been accorded authority for making certain value judgments, only in recent times has the evaluation of public programs become so formalized as to constitute a recognizably separate activity — and even a new discipline. (House, 1980, p. 15)

Evaluation may or may not be a new discipline as House suggests but it certainly has emerged over the past twenty-five years as a substantial field of activity with a wide range of models and approaches and its own criteria, principles and standards. The field has developed extremely quickly in response initially to the need to monitor large scale social programmes and more latterly to the need to inform policy deliberations at different levels of educational action and accountability.