Results for U.S. students and adults on international assessments vary by subject, grade or age, and assessment. Although it would be desirable, it is not possible to directly compare the international assessment scores from the various studies because of differences in the countries participating, the purpose of the assessments, the items used, and the target populations. Without making direct comparisons between studies, the following section presents highlights of the key findings of several recent international studies that looked at students’ and adults’ achievement in reading, mathematics, and science.