Multiage grouping refers to "a class grouping in which students of different ages and identified age levels are grouped together in a single classroom for the purpose of providing effective instruction" (Miller, 1995, p. 29). The multiage environment is deliberately created for the benefit of children, not because of economic needs or declining enrollment. The intention is to allow children of various ages and abilities to progress at their own individual rate rather than according to specified objectives for a particular grade level.
A multiage class is not the same as a combination class (sometimes called a split class), however. In a combination class, two or more grade levels are placed together in the same classroom but the teacher teaches a separate curriculum for each grade. A combination class often is created when a school has declining enrollment for two or more grade levels.
For more information on multiage grouping, refer to the following sources: