How much does class size reduction improve achievement?

The STAR study found reducing class size from 22-26 to 13-17 students in K-3 produced 4-8 percentile point gains, with benefits persisting through high school.

Is class size reduction cost-effective?

Class size reduction is expensive (requires 40% more teachers) but produces lasting effects. Other interventions like high-quality tutoring often produce comparable gains at lower cost.

Who benefits most from smaller classes?

Students from disadvantaged backgrounds and early grades (K-3) show the largest class size benefits. High-achieving students in middle and high school show minimal marginal gains.

Class Size Reduction Achievement Impact

Formula Definitions

The Class Size Reduction Achievement Impact works by applying a well-defined formula to the values you enter. Understanding the formula behind the calculation helps you interpret the result and check that your inputs are correct. Below we break down the key components that drive the Class Size Impact.

The core formula used by this calculator is:

Result = f(inputs, settings)

Each variable in the formula has a specific meaning:

inputs — Values entered into the Class Size Impact.
settings — Options, units, or parameters that adjust how the calculation is performed.
Result — Computed output for the chosen inputs and settings.

How to Use This Calculator

Enter the required values. Enter the required values into the Class Size Reduction Achievement Impact input fields.

Adjust settings. Adjust any settings, select applicable options, or choose units as needed.

Calculate the result. Press Calculate to compute the result using the underlying formula.

Interpret the output. Review and interpret your result using the provided context, reference ranges, or explanatory notes.

Glossary and Definitions

Input

A value entered into the calculator to be processed.

Output

The computed result returned by the calculator for the given inputs.

Setting

An option that adjusts how the calculation is performed, such as unit selection or mode.

Class size reduction

A key concept referenced by the Class Size Impact: Estimate the academic achievement gain from reducing class size using effect size data from the Tennessee STAR experiment and Project SAGE.

Class size effect

A key concept referenced by the Class Size Impact: Estimate the academic achievement gain from reducing class size using effect size data from the Tennessee STAR experiment and Project SAGE.

STAR study

A key concept referenced by the Class Size Impact: Estimate the academic achievement gain from reducing class size using effect size data from the Tennessee STAR experiment and Project SAGE.

Small class achievement

A key concept referenced by the Class Size Impact: Estimate the academic achievement gain from reducing class size using effect size data from the Tennessee STAR experiment and Project SAGE.

Class Size Reduction Achievement Impact

Formula Definitions

How to Use This Calculator

Glossary and Definitions

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Frequently Asked Questions