Grouping: What the Research Says
- Students at all achievement levels (high, medium and low) benefited from cluster grouping and other forms of instructional grouping accompanied by differentiated instruction and content. Students who were in cluster groups scored significantly higher than students who did More students were identified as high achieving during the three years that cluster grouping was used in the school. 
- Achievement is increased when gifted and talented students are grouped together for enriched or accelerated learning. Ability grouping without curricular acceleration or enrichment produces little or no differences in student achievement. Bright, average, and struggling students all benefit from being grouped with others in their ability/instructional groups when the curriculum is adjusted to the aptitude levels of the group. When gifted students are grouped together and receive advanced enrichment or acceleration, they benefit the most because they outperform control group students who are not grouped and do not receive enrichment or acceleration by five months to a full year on achievement tests. 
- Grouping gifted and talented students for instruction improves their achievement. Full-time ability/instructional grouping produces substantial academic gains in these students. Pullout enrichment grouping options produce substantial academic gains in general achievement, critical thinking, and creativity. Within-class grouping and regrouping for specific instruction options produce substantial academic gains provided the instruction is differentiated. Cross-grade grouping produces substantial academic gains. Several forms of acceleration also produced substantial academic effects. Cluster grouping produces substantial academic effects. 
- Treatment group students who were grouped for an enriched math lesson and exposed to an enhanced math unit had significant differences on their math achievement when compared to the comparison groups. Further, results indicated significant differences favoring the group that received a modified and differentiated curriculum in a grouped class. 
Grouping is Not Tracking
Read a commentary by NAGC president Paula Ollszewski-Kubilius on Setting the Record Straight on Ability Grouping found in Education Week Teacher, May 20, 2013.
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 Gentry, M.L., & Owen, S.V. (1999). An investigation of the effects of total school flexible cluster grouping on identification, achievement, and classroom practices. Gifted Child Quarterly, 43, 224 - 243.
 Kulik, J. A. (1992). An analysis of the research on ability grouping: Historical and contemporary perspectives (RBDM 9204). Storrs: University of Connecticut, the National Research Center on the Gifted and Talented.
 Rogers, K. B. (1991). The relationship of grouping practices to the education of the gifted and talented learner (RBDM 9102). Storrs: University of Connecticut, the National Research Center on the Gifted and Talented.
 Tieso, C. L. (2002). The effects of grouping and curricular practices on intermediate students' math achievement (RM02154). Storrs: University of Connecticut, the National Research Center on the Gifted and Talented.