This paper reports the accuracy with which students report their high school grades and nonacademic achievements when they write the ACT Test Battery. A sample of 5,775 student records from 134 high schools was studied. The correlations between self-reported and school-reported grades were found to range from .81 to .86. The correlations were examined separately for "overreporters," and "accurate reporters" in terms of a number of student characteristics: ability, race, sex, class rank, parents' income level, students' level of aspiration, and class size. The accuracy with which the self-reported information was collected was stable over income levels, sex, race, and size of class. Students who aspire for less than a bachelor's degree tend to overreport their grades more than students who aspire to at least a bachelor's degree. Students also tend to accurately report their nonacademic achievements. The accuracy of self-report on these items is comparable to that of high school grades, in that accuracy did not seem to vary with student background characteristics. (Author)