A number of recent policies have tried to improve science learning by increasing the number of science courses required for high school graduation or admission to higher education institutions. But it is highly unlikely that these mandates alone will materially affect the amount and quality of science education for students. Any effort to improve the outcome of science education must carefully consider the effectiveness of the science curriculum. This paper examines options for improving the science curriculum based on research, best extant practices and experience in other countries. Although the word "curriculum" has acquired many different meanings, both in the professional literature and in lay usage, this paper defines curriculum as the intended substantive and pedagogic content of science education to be presented to students in order to develop their knowledge and skills. [This document is a reissue of the July 1988 CPRE Research Report RR-006 under the same title (ED297956).]