Twin aims--to advance theory and to improve practice in science, mathematics, and computing education--guided the Educational Technology Center's (ETC) research from its inception in 1983. These aims led ETC to establish collaborative research groups in which people whose primary interest was classroom teaching and learning, and researchers concerned primarily with developing and testing theory, would keep each other honest. Several such groups identified targets of difficulty in the K-12 science, mathematics, and programming curricula and proceeded to develop experimental approaches including new technologies to improve teaching of these conceptually difficult topics. Most groups began with close observations of individual students and progressed to design materials and activities for teaching experiments which they conducted first with small groups and then with whole classrooms. Three of ETC's research groups had the following proposals: (1) using microcomputer based laboratory equipment and other technologies to teach students about heat and temperature; (2) infusing a programming "metacourse" into introductory classes in BASIC; and (3) teaching with the "Geometric Supposers" to incorporate inductive reasoning into traditional geometry courses. Included are goals, approaches, and implementation requirements of the innovations; discussion of the laboratory sites; and findings for introducing and integrating new technologies. (MVL)