Federal regulations indicate that the achievement gap must be closed between subgroups, including the gap between special education and non-special education students. We explored the ways in which achievement trends are influenced by three methods of reporting (cross-sectional, cohort-static, and cohort-dynamic). We also investigated (a) the ways in which achievement gaps change when different analytical techniques (proficiency levels, scale scores, effect size) are used, and (b) the relationship between student achievement and the extent to which students' special education status changes across years. We conclude by discussing the practical and policy implications of using the three methods for reporting data about the performance gap.