The impact of cohort changes with regard to ethnic group, gender, class rank, and first language learned on yearly average Scholastic Aptitude Test (SAT) and Test of Standard Written English (TSWE) scores was studied. All examinee records, including student test scores and student responses to the Student Descriptive Questionnaire, in the College Board Seniors data sets for 1985 and for 1987 through 1990 were analyzed. Data are provided in the following categories: ethnic group (American Indian, Asian-American, Black, Hispanic, White, and other), gender (52% female and 48% male for each of the 5 years studied), class rank (top 10th, second 10th, second fifth, third fifth, fourth fifth, and fifth fifth), and first language learned (English, English and another, and another). Regression and cross-classification analyses were conducted. Both analyses adjusted test score means based on common cohorts of students. The SAT and TSWE means for the last 3 years may have been higher if changes in the cohort had not occurred. Approximately half of the decline in SAT verbal (SAT-V) scores was associated with cohort change. Average SAT mathematics (SAT-M) scores could have risen by three points, rather than remaining constant, if the 1987 and 1990 cohorts had remained the same. Two figures and three data tables are included. Three appendices list the means of students cross-classified by gender, ethnic group, and class rank for SAT-V, SAT-M, and TSWE. (RLC)