RIGOROUS COURSES RESEARCH FINDING: The stronger the emphasis on academic courses, the more advanced the subject matter, and the more rigorous the textbooks, the more high school students learn. Subjects that are learned mainly in school rather than at home, such as science and math, are most influenced by the number and kind of courses taken. COMMENT: Students often handicap their intellectual growth by avoiding difficult courses. In order to help young people make wise course choices, schools are increasingly requiring students to take courses that match their grade level and abilities; schools are also seeing to it that the materials used in those courses are intellectually challenging. The more rigorous the course of study, the more a student achieves, within the limits of his capacity. Student achievement also depends on how much the school emphasizes a subject and the amount of time spent on it: the more time expended, the higher the achievement. Successful teachers encourage their students' best efforts. Chall, J., Conard, S., and Harris, S. (l977). An Analysis of Textbooks in Relation to Declining SAT Scores. New York: Col- lege Entrance Examination Board. Ginsburg, A., Baker, K., and Sweet, D. (l98l). "Summer Learning and the Effects of Schooling: A Replication of Heyns." Paper presented at the Annual Meeting of the American Educational Research Association, Los Angeles, CA. ERIC Document No. ED 204367. Holsinger, D., (l982). "Time, Content and Expectations as Pre- dictors of School Achievement in the USA and Other Developed Countries: A Review of IEA Evidence." Paper presented to the National Commission on Excellence in Education, New York. ERIC Document No. ED 227077. Pallas, A. M., and Alexander, K. L. (Summer l983). "Sex Differ- ences in Quantitative SAT Performance: New Evidence on the Differential Coursework Hypothesis." American Educational Re- search Journal, Vol. 20, No. 2, pp. l65-l82. Walberg, H. J., and Shanahan, T. (l983). "High School Effects on Individual Students." Educational Researcher, Vol. l2, No. 7, pp. 4-9.