This research aimed to examine the strategy effectiveness of the Integrating Inquiry-based learning and Student Teams Achievement Division (INSTAD) compared to other strategies: Inquiry; Student Teams Achievement Division (STAD); and conventional learning, in order to narrow Upper Academic Ability (AA) and Lower Academic Ability (AB) science students’ learning outcome gap. As many as 136 research subject, consisting of AA and AB 7th grade students in equal numbers were selected using stratified random sampling from 27 State Junior High Schools in Surakarta, Indonesia. This research employed 4x2 factorial design as a method. Students’ learning results were measured with an essay test, then analyzed using Anakova. Findings demonstrate that INSTAD is the optimum strategy to constrict AA and AB students’ science grade point average, compared to Inquiry, STAD, and conventional learning.