A variety of methods can be used for instructing classes having highly heterogeneous students, including individualization of instruction, homogeneous grouping, team teaching, and modifying whole-class instruction. Through classroom observations and teacher interviews, the prevalence of such methods in 32 second- and third-grade classrooms were studied, and the relationships between these methods and student achievement were examined. A greater variety of approaches to heterogeneity was observed in reading instruction than in mathematics instruction. Very few relationships were found between use of the various approaches and achievement gains in mathematics. In reading, however, greater achievement gains were associated with the extent of team teaching arrangements, use of individualized instruction, and several other variables. (Author/JD)