This report from The Nation's Report Card provides further information about students' lack of preparation in science, their apparent disinclination to enroll in challenging science courses, and the comparatively low achievement of Back and Hispanic students, females, economically disadvantaged students, and non-college bound students. These Science Report Card results are based on a national survey of nearly 20,000 students in grades 4, 8, and 12, conducted during the winter and spring of 1990 by the National Assessment of Education Progress (NAEP). The results from the 1990 science assessment were analyzed using item response theory (IRT) methods, allowing NAEP to describe performance across the grades and subpopulations on a 0 to 500 scale. Along this continuum, four levels of proficiency were defined: Level 200: Understands Simple Scientific Principles; Level 250: Applies General Scientific Information; Level 300: Analyzes Scientific Procedures and Data; and Level 350: Integrates Specialized Scientific Information. Overall science proficiency by race/ethnicity, gender, region, type of community, type of school, parents' highest level of education, additional home factors, types of high school programs, and plans after high school was determined. Chapters include: (1) "Overall Science Proficiency for the Nation and Demographic Subpopulations"; (2) "Levels of Science Proficiency for the National and Demographic Subpopulations"; (3) "Science Proficiency by Content Areas for the Nation, Subpopulations, and in Relation to High School Course-Taking"; (4) "Attitudes toward Science Education and Students' Experiences in Science"; (5) "Toward Scientific Literacy for All: Instructional Goals and Practices"; and (6) "Who Is Teaching Science? A Profile of the Eighth-Grade Science Teaching Force." The profile survey on teachers included data on race/ethnicity, years of teaching experience, level and type of teaching certification, academic training, teachers' perceptions of their preparation to teach science topics, and teachers' professional activities in science. An overview of the procedures used in the 1990 science assessment, the NAEP scale anchoring process for the 1990 science assessment and additional example anchor items, and statistical data for all parts of the survey are appended. (KR)