This longitudinal study of 78 Canadian English-speaking students examined the applicability of the stability, cumulative, and compensatory models in reading comprehension development. Archival government-mandated assessments of reading comprehension at Grades 3, 6, and 10, and the Canadian Test of Basic Skills measure of reading comprehension administered at Grade 10 were used. The probabilities of later-grade reading achievement based on earlier-grade reading achievement were computed, and tests of regression to the mean were conducted. Most changes in relative achievement were attributed to regression toward the mean. Overall, results suggest considerable stability across time.