This report summarizes data from the National Assessment of Educational Progress (NAEP), which has been monitoring the scholastic achievement of America's 9-, 13-, and 17-year-olds since 1969. The 1990 NAEP trend data provide several ways of describing changes in student achievement in each curriculum area. For science, mathematics, and reading, the NAEP has used proficiency scales developed through item response theory to summarize student achievement across questions and to give a basis for describing overall student achievement in each area. Trends are presented for science, mathematics, reading, and writing overall, and for the following demographic subpopulations: (1) racial and ethnic groups (White, Black, and Hispanic American students); (2) gender; and (3) region (Northeast, Southeast, Central, and West). Trends in percentages of student at or above proficiency levels are summarized for five levels for each subject area. Comparative statistics are provided for selected NAEPs between 1970 and 1990. Thirteen figures show trends for the subject areas in graph form. (SLD)