Compared were the effectiveness of individualized instruction in a mainstreamed open classroom setting and instruction in a traditional classroom setting on the achievement levels of 56 low ability students (grades 1-6). Two groups of Ss, paired for grade level and IQ, were tested after 1, 2, and 3 years of exposure to the models. There was no significant difference in academic achievement scores of the two groups; however, the expected corresponsence between IQ and achievement was found. (IM)