The Tennessee STAR Project is one of the most well-known educational evaluations conducted in the United States. Implemented in the 1980s, it examined whether reducing class sizes in early grades (K–3) would improve student achievement. Students and teachers were randomly assigned to one of three conditions:

Small classes (13–17 students)

Regular classes (22–25 students)

Regular classes with a teacher aide

Researchers then tracked students’ academic performance, attendance, and long-term outcomes such as high school graduation rates. The data spanned several years, making the project a large-scale, longitudinal evaluation.

Strengths of the Tennessee STAR Evaluation
1. Strong research design

The use of randomized controlled trials (RCTs)—the gold standard in research—minimized bias and allowed clear comparisons between groups.

Findings were highly credible and widely accepted due to the rigorous design.

2. Long-term data collection

Researchers followed students for years, enabling them to assess both immediate and lasting impacts of class size reduction.

This long-term lens revealed that early intervention benefits persisted into adulthood.

3. Policy relevance

Results directly influenced educational policy across the U.S. and internationally.

Many states used STAR evidence to justify funding for smaller class sizes.

4. Large sample size

Thousands of students and teachers participated, making the findings generalizable across diverse contexts.

Weaknesses of the Tennessee STAR Evaluation
1. Limited contextual analysis

While the study measured achievement outcomes, it gathered less qualitative data on student engagement, teacher strategies, or classroom climate.

This made it harder to understand why smaller classes were effective.

2. Implementation inconsistencies

Some schools could not strictly maintain class size limits or student assignments, causing overlap between groups.

Such deviations may have diluted the treatment effects.

3. Cost and scalability issues

Class-size reduction is expensive, and not all schools or districts can afford it.

STAR demonstrated effectiveness, but it did not fully address feasibility in low-resource settings.

4. Focus on traditional academic outcomes

The evaluation prioritized test scores over other competencies such as social-emotional development or collaborative skills.

This limits the interpretation of “student success” to narrow academic indicators.