Combination Classes and Student Achievement

Policy Analysis for California Education

The combination class, in which students from two adjacent grades are grouped within one classroom under one teacher, is a tool that school administrators can use to manage uneven class sizes and conserve scarce facility and personnel resources. If combination-class membership has a nonnegative effect on student outcomes, offering them could be an attractive strategy for schools looking to save money without sacrificing educational quality.

In a recent study published in Economics of Education Review, Jaime Thomas, a researcher at Mathematica Policy Research, analyzes the relationship between combination class membership and academic achievement in first grade. She finds that first graders in combination classes do no better and no worse than their single-grade counterparts on reading, math, and general knowledge tests given at the end of the school year. In addition, she finds no evidence that first graders in schools offering combination classes perform worse than first graders in similar schools that do not offer such classes, indicating that combination classes may be a viable cost-saving option for school administrators.

Thomas uses data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 (ECLS-K) and considers first graders in single-grade and K1 and 12 combination classes. She shows that schools offering combination classes appear to be more disadvantaged than single-grade schools, are more likely to be located in the western part of the U.S., and are more likely to have a year-round calendar. Combination teachers are similar to single-grade teachers on most measures with a notable difference being that K1 teachers have more teaching experience. Thomas provides evidence that more academically advanced students are selected for 1-2 classes: these students had higher kindergarten test scores than students who ended up in single-grade or K1 classes in first grade.

Using several different methods to control for cross-school differences and for factors that influence student assignment to a combination class, as well as comprehensive controls for student and teacher characteristics, Thomas finds no relationship between combination-class membership and first-grade scores on reading, math, and general knowledge tests. Considering school-wide first-grade achievement, the study compares scores in schools offering only single-grade first-grade classes and those offering combination classes, finding no significant differences.

Thomas notes that she cannot rule out the existence of bias from unobservable differences between combination and single-grade students or teachers. She also notes that, since her sample of schools is small and since she only considers first grade, her results may not be generalizable to other settings. Despite these caveats, this study is notable in its contrast to other studies that have found negative associations between combination classes and achievement, and it highlights the importance of accounting for cross-school differences.

The full study is in Thomas, Jaime L. (2012). “Combination Classes and Educational Achievement.” Economics of Education Review, vol. 31, no. 6, pp. 1058-1066.


Suggested citationPolicy Analysis for California Education. (2013, March). Combination Classes and Student Achievement [Commentary].