The nature of classroom learning environments created by teachers had been considered very important for learning to take place effectively. This study investigated the effect of creating constructivist and transmissive learning environments on achievements of science students' of different ability levels. 243 students formed the entire study sample, while 146 (70 high and 76 low ability) students took part in the ability groupings. Three research instruments (teaching guides; scholastic ability test and Basic science achievement test), were used to obtain data for which two research hypotheses were tested. The validation and reliability of the instruments were fully established. Results indicate that students in the constructivist environment achieved more. And that the high ability students irrespective of their learning environment achieved more than the low ability students which indicates that learning environments do not have impact on learning ability. However, since the high and low constructivist groups achieved more than the high and low transmissive groups respectively, it is recommended that teachers should create the constructivist environment while paying extra attention to the low ability groups in order to reduce gaps between high and low ability during their basic science classes in Nigeria.