Faced with increasing numbers of mildly handicapped students, schools are implementing a variety of instructional arrangements to serve them. This study examined the extent to which different instructional grouping arrangements are used for different categories of mildly handicapped students in different instructional settings and the extent to which any differences are translated to differences in student responses. Observational data were recorded all day in 10-second intervals for 30 mentally retarded, 30 learning disabled, 32 emotionally/behaviorally disturbed, and 30 nonhandicapped students. While handicapped students, in general, received more individualized instruction, usually in the special education setting, the only category effect that emerged was that educable mentally retarded (EMR) students in self-contained placements spent a greater proportion of special education time in entire group instruction. Differences in instructional grouping arrangements translated to differences in student responding, with active responding and academic engaged rimes significantly higher during individual instruction, compared to entire group and small group instruction, in both mainstream and special education settings. Implications for classification practices are discussed. © 1988 Taylor & Francis Group, LLC.