Achievement Gap and Tracking, International Evidence

Tracking groups students on the basis of academic ability or achievement. It also involves curriculum differentiation, presenting higher-achieving groups of students with more advanced academic content than their lower-achieving peers. Proponents of tracking and closely related practices argue that they facilitate all students' learning by providing students with course material well matched to their current skills and knowledge. However, others oppose tracking, believing that it increases the achievement gap between initially higher-and lower-achieving students. For example, they suggest that classes consisting entirely of low-achieving students may be less conducive to learning than those including higher-achieving students. They also point out that the less challenging curricular materials presented in low-achieving classes could well produce less learning than the more advanced content covered elsewhere, even for low-achieving students. Such outcomes would have important implications for students from immigrant, minority, and low-income backgrounds because they are disproportionately found in lower-achieving tracks in many countries. Thus, research on the impact of tracking on the achievement gap between initially lower- and higher-achieving students is crucial to resolve this debate.

Much of the research on this topic has been conducted in the United States. However, research from other developed countries is also very useful in addressing basic questions regarding whether and how tracking and similar practices contribute to the achievement gap. For example, such research allows study of very strong forms of tracking not found in the United States, such as Germany's tiered schools. In addition, multicountry studies allow exploration of (a) the amount of curriculum differentiation in an educational system, (b) the age at which differentiation starts, and (c) whether the number of tracks or tiers found in school systems are related to the size of the achievement gap. Existing reviews of the literature typically focus heavily on U.S.-based research, often underutilizing research from other developed countries. To redress this imbalance, this entry summarizes the results of research from other developed countries, focusing on that conducted in secondary schools because tracking and similar practices are most common there. It concludes that having high-ability or high-achieving schoolmates/classmates is associated with increased achievement, controlling for individual students' initial achievement. It also supports the conclusion, common in U.S.-based research, that grouping by ability accompanied by curriculum differentiation is related to an increased achievement gap between initially higher- and lower-achieving students.

Grouping on the basis of ability and curriculum differentiation are clearly not identical. Each may well have its own independent effects. In practice, however, they are closely intertwined because groups of academically stronger students typically get more advanced curricula in schools with differentiated curricula. Thus, it is often difficult to determine how much of any impact of tracking found stems from each of its two individual components. However, some research focuses on the impact of each of these factors separately. It, as well as research focusing on the combined effect of grouping by ability and curriculum differentiation, is discussed in this entry.

Serious methodological issues arise when trying to determine the impact of grouping by ability and curriculum differentiation on students' learning. For example, unmeasured individual variables that might lead both to placement in high-ability groups and to unusually high achievement gains could suggest a spurious conclusion that placement in a high-ability class or school causes increased achievement. Fortunately, the studies on which this entry is based are typically strong methodologically and statistically. For example, most of them take the crucial step of controlling for the individual student's initial achievement when assessing the relationship between peers' average ability and individual achievement gains. Also, many try to minimize or control for mean peer socioeconomic status (SES) and/or curriculum differences so that effects stemming from such differences are not mistakenly attributed to mean ability levels. However, caution is nonetheless appropriate in interpreting the results of these studies given the complexity of the issues involved and the difficulty in ruling out all possible threats to the validity of these studies' conclusions.

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