Describes how principals assign teachers and students to single-grade and combination classes. Presents research showing unexpected constraints that fundamentally changed the basis of class assignment and, consequently, the nature of classroom compositions. A case is made that multitrack calendars reduce principals' flexibility to make purposive…

S. Veenman argues that his reviews of the literature lead to the conclusion that combination classes are neither worse nor better than single-grade classes. This rejoinder discusses disagreements with Veenman's findings, which are hampered by a narrow reading and interpretation of the literature on potential positive effects of combination…

Research on combination classes, in which students from two or more grades are placed with one teacher for most or all of the school day, is reviewed. Consistent research findings are that combination classes, distinguished from multiage/nongraded classes, have at least a small negative effect on student achievement. (SLD)