Presenting data and analyses from the first wave of the study "High School and Beyond" (HS&B), a longitudinal study of United States high school sophomores and seniors, the report focuses on the composition of the Hispanic tenth and twelfth grade student population with respect to various characteristics; i.e., language use and proficiency, length of U.S. residence, family's socioeconomic status. The first section describes differences among Hispanic subgroups, and between Hispanics and the rest of the student population, with respect to both measures of achievement (school delay, aspirations, test scores) and possible explanatory factors (language usage, socioeconomic status, immigration history). The next section presents a basic model of the educational achievement process for Hispanics to investigate the relative importance of the basic input factor (language use and proficiency, family socioeconomic status, length of U.S. residence) as determinants of Hispanic educational attainment, and to explore whether differences in achievement profiles of Hispanic subgroups, which are previously noted, can be explained by subgroup differences in these basic input factors. Prior to presentation of the results, the HS&B data, selection of samples, and other methodological aspects of the study are discussed. Selected questions on language use, language proficiency, and national origin are appended. (NQA)