The authors question whether elementary students will have access to effective science and mathematics instruction within the current structure of elementary schools, in which each classroom teachers is expected to possess the expertise to teach all subjects well. They review research showing that good teachers are the key to student achievement and that science and mathematics lessons in elementary schools generally lack the characteristics of effective instruction. They propose the Collaborative Specialists model to restructure elementary school instruction. Under this model, schools form collaborative teaching teams in which teachers who have proven expertise in science, mathematics, or another content area provide instruction for all students in that subject. (Contains 1 endnote and 1 figure.)