Four variables have been identified by research as having a powerful influence on teachers' teaching practices and student learning. These are: (1) content coverage; (2) content exposure; (3) content emphasis; and (4) quality of instructional delivery. These four variables are important to the investigation of students' opportunity to learn science in U.S. classrooms. Current instructional practices systematically place certain groups of students at a disadvantage, and the goal of scientific literacy for all students cannot be met. Two models of learning, cooperative learning and constructivism, have been effective in helping poor and minority students to achieve. While there is an abundance of information about improving students' opportunity to learn, there is still a disconnection between research knowledge on improving academic achievement through addressing opportunity to learn and the implementation of knowledge in classrooms. Connecting this knowledge and practice is enhanced by the realization that teacher education makes a difference in producing the environment conducive for learning. In addition, teacher collaboration brings support for teachers to try new approaches. Teachers who are working in communities of professionals sustain change in classrooms. It is also apparent that teaching and learning must include teachers who are learning. Teacher learning begins with preservice teacher education, which must include courses in cognitive psychology, developmental psychology, learning theory and pedagogy, and professional ethics. Teacher inservice education is also important. Educators must use the information provided by educational research. Science standards are important to the process of science education reform, but these standards must encompass expectations for teachers to upgrade their content knowledge and teaching skills through preservice and inservice education. (Contains 14 references.) (SLD)