The effect of a basic competency education program on the achievement of high, average, and low-achieving students was examined for the Alabama Basic Competency Education program (BCE). California Achievement Tests scores in reading, mathematics, and language were examined for 3 years prior to initiation of the BCE program and for 3 years afterward. Three analyses were conducted: (1) statewide achievement levels, in terms of normal curve equivalents (NCE), were analyzed before and after BCE; (2) school systems were categorized as high-achieving, average-achieving, or low-achieving, and NCEs were analyzed for each type of system before and after BCE; and (3) individual students classified as above average, average, or below average were analyzed for 3 years following BCE. CAT scores for 1974-1976 represented the achievement levels prior to BCE while 1981-1983 scores represented achievement levels after BCE; data were not available for 1977-1978 and 1979-1980, which were considered to be transitional implementation years. Results indicated significant improvement in student achievement concomitant with the initiation of the BCE program, especially for the first and second analyses. The third analysis indicated decreasing achievement from 1981 to 1983 and an increase from 1983 to 1984. (GDC)