While assessment may be a useful source of leverage on the system as a whole, its impact on individual pupils and their attitude to education continues to be a source of grave concern in many countries. The key role that assessment plays in selection makes the public legitimacy and reliability of such procedures an overriding concern and a frequent barrier to the introduction of a range of classroom-based assessment techniques. Little can be done to remove the well-recognized shortcomings of many public examinations in countries where it is this kind of assessment that is to determine the small proportion of a given age-group who will be allowed to continue their studies. In countries where educational opportunity does not need to be so severely rationed, it is still frequently used to support a hierarchy of higher and lower status institutions, with the result that legitimacy and perceived reliability retain their critical importance. Only where the more pressing problem is a shortage of suitably qualified candidates rather than the need to select, are such concerns typically giving way to a greater emphasis on validity and assessment techniques that encourage the development of new skills and competencies among young people.