The importance of changing teachers' beliefsand practices in school improvement efforts iswell accepted but little empirical work hasbeen reported on the micro-processes involved.In this paper, we use schema theory to examinehow the teachers in three schools changed theirbeliefs about the causes of low academicachievement from external factors, such as theparents' and children's deficits, to internalfactors, such as the contribution of their ownteaching practices. These change processes arecontrasted briefly with those in a fourthschool in which the teachers continued to blameexternal factors. The three conditionsidentified as critical for schema revisionincluded the salience of discrepant data, thepresence of an external agent to assist withthe interpretation of those data, and theavailability of information on alternativepractices.