This study examined the relationship between developmentally appropriate and traditional teaching methods and the mathematics achievement of 15 average and 10 students with disabilities. Data were collected in four first grade classes, one second grade class, and one multi-age inclusion program. A descriptive research design was used with observations, interviews, and questionnaires. Principal component methods were used to generate continuous composite variables that described teacher presentation, materials, grouping, and curriculum. The outcome measure was a curriculum-based measure of mathematics achievement. Analysis found that variables characterizing the developmentally appropriate versus traditional continuum were not associated with mathematics achievement. For both general and special education students, achievement was associated with measures of student mathematical processing and strategy instruction. Use of abstract mathematics-only manipulative materials and math worksheets was negatively related to achievement. The findings suggest the debate about developmentally appropriate versus traditional practices is not fruitful. Nine tables of data are appended. (Contains 31 references). (Author/JLS)