This study investigated how the 1998 Iowa Tests of Basic Skills (ITBS) achievement test scores of retained students in third grade (15% of students tested), sixth grade (10%), and eighth grade (4.6%) affect the citywide results in those grades and in subsequent grades. In third, sixth, and eighth grades, when the scores of retained students are removed, the 1998 test scores become higher than reported in both reading and mathematics. In fourth and seventh grades (a ninth grade analysis was not possible), when the retained students were included s if they had taken the test in those grades, the scores became lower than reported. Compared with 1997 scores, the adjusted third, sixth, and eighth grade scores were up, and the fourth and seventh grade scores, with the exception of seventh grade mathematics, are not. Even after those adjustments, the overall systemwide scores were still up from 1997. Did the promotion/retention policy seriously distort the 1998 ITBS test score results? In the opinion of the researchers, it did not. The study also shows that grouping students by age instead of grade is a viable alternative for tracking their scores. The age groupings mirror the grade group findings, with the greatest improvements among students most directly affected by the policy. This procedure is expected to be useful in the future as the composition of grades becomes increasingly complex. (Contains 12 figures, 4 tables, and 4 endnotes.) (SLD)