This investigation was undertaken to provide insights as to how to improve the quality and relevance of teacher training in grading practices. The study was designed, by looking at grading practices of 15 high school teachers via intensive case study methodology, to explore: (1) the nature and technical quality of assessment and grading practices; and (2) why professional training has had so little impact. The researchers prepared a comprehensive framework of 34 grading issues to serve as a basis for observing teachers' grading practices. Information was gathered from each of the teachers in relation to the questions about grading practices. Seven questions focused on basic assumptions or antecedents that feed actual grading practices; twenty dealt with grading practices themselves; and the remainder addressed issues of the effects of grading. Discrepancies between best practices and actual practices were noted in 26 of the issues. An analysis of possible causes for the discrepancies revealed that 21 of the 26 practices probably have multiple causes. Recommended practice may need to be reevaluated in light of the realities of the classroom, and training in sound grading practices for teachers and principals is needed. (Results are presented for each issue, and reasons for discrepancies between recommended and actual practice are listed in chart form.) (LMO)