Diverse students learning in a morphing classroom.

Rethinking Education: Why Class Size Isn't the Only Thing That Matters

Mira Elwood in Mind & Education June 2025 • 4 min read.

"Unpacking the hidden complexities of class size reduction and its real impact on student learning."

In an era defined by data-driven decisions and evidence-based policies, the pursuit of effective educational strategies has never been more critical. Randomized controlled trials (RCTs) have emerged as a cornerstone of this movement, promising to deliver unbiased insights into what truly works in the classroom. But what happens when the quest for scientific rigor overshadows the real-world complexities of education? Can a narrow focus on isolated factors lead us down the wrong path, overlooking the bigger picture of student success?

Enter Project STAR, a landmark study that sought to determine the impact of class size on student learning. The findings ignited a wave of class size reduction (CSR) initiatives across the United States. But as these policies unfolded, unexpected challenges arose, leaving many to question whether smaller classes truly translated into better outcomes. What went wrong? And what can we learn from this experience to create more effective and equitable education policies?

This article takes a closer look at the hidden complexities of class size, challenging the notion that smaller is always better. We'll delve into the limitations of Project STAR, explore the importance of considering the broader educational ecosystem, and uncover alternative approaches to fostering student success. Get ready to rethink education and discover the surprising truths about what really matters in the classroom.

The Project STAR Paradox: When Rigor Meets Reality

Diverse students learning in a morphing classroom.

Project STAR, a large-scale RCT launched in Tennessee, seemed like the perfect recipe for evidence-based policy. By randomly assigning students to classes of different sizes, researchers aimed to isolate the impact of class size on test scores. The results appeared promising: smaller classes, particularly in the early grades, led to improved student performance. But as states rushed to implement CSR policies, the anticipated benefits often failed to materialize.

One of the key limitations of Project STAR was its narrow focus on a single variable: class size. While the study meticulously controlled for other factors, it failed to account for the complex interplay of elements that shape student learning. Factors such as teacher quality, curriculum design, and parental involvement were largely overlooked, creating a distorted picture of the true impact of CSR.

Here are some critical factors often missed when focusing solely on class size:

Teacher Quality: Reducing class size without ensuring qualified teachers can dilute the benefits.
Resource Allocation: Funds spent on CSR might be better used for resources or technology.
Curriculum Design: A smaller class doesn't automatically mean a better learning environment.
Student Diversity: Ignoring the diverse needs of students can undermine any class size benefits.

Moreover, Project STAR's emphasis on average effects obscured the significant variations in how class size impacts different students. Some students thrive in smaller settings, while others benefit from the dynamic interaction of larger groups. Ignoring this heterogeneity can lead to one-size-fits-all policies that fail to address the diverse needs of learners.

Beyond Class Size: A Holistic Approach to Education

The lessons of Project STAR underscore the importance of taking a holistic approach to education. Instead of fixating on isolated variables, policymakers and educators must consider the complex interplay of factors that contribute to student success. By investing in teacher development, creating engaging curricula, fostering parental involvement, and addressing the unique needs of each learner, we can create more effective and equitable learning environments for all.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.2139/ssrn.2888198, Alternate LINK

Title: Economic Research And Education Policy: Project Star And Class Size Reduction

Journal: SSRN Electronic Journal

Publisher: Elsevier BV

Authors: Moshe Justman

Published: 2016-01-01

Everything You Need To Know

What was Project STAR and what were its main findings regarding class size and student performance?

Project STAR was a large-scale, randomized controlled trial conducted in Tennessee. It aimed to determine the impact of class size on student learning by randomly assigning students to classes of different sizes. The study found that smaller classes, particularly in the early grades, led to improved student performance as measured by test scores. However, its narrow focus on class size as the primary variable has been criticized for overlooking other important factors.

What are some of the challenges in implementing class size reduction (CSR) policies effectively, even when inspired by studies like Project STAR?

While Project STAR suggested benefits from class size reduction (CSR), implementing such policies can be complex. A key challenge is ensuring that reducing class size doesn't dilute the quality of teaching. Without qualified teachers, the potential gains of smaller classes may not materialize. Additionally, the financial resources allocated to CSR might be more effectively used for other interventions like improving curriculum design or investing in educational technology. Addressing student diversity is also crucial, as a uniform approach to class size may not cater to the unique needs of all learners.

What key factors did the Project STAR study overlook in its assessment of the impact of class size on student learning?

The Project STAR study primarily focused on the impact of class size on student test scores, particularly in the early grades. However, it didn't fully account for factors like teacher quality, curriculum design, parental involvement, and the diverse needs of individual students. By overlooking these interconnected elements, the study provided a limited view of what truly drives student success. A more holistic approach would consider how these factors interact to create effective learning environments.

What does it mean to take a holistic approach to education, and how does it differ from focusing solely on class size?

A holistic approach to education moves beyond a singular focus on factors like class size and considers the complex interplay of various elements that contribute to student success. This involves investing in teacher development to enhance the quality of instruction, creating engaging and relevant curricula, fostering parental involvement to support learning at home, and addressing the diverse needs of all learners through personalized instruction and targeted interventions. By considering all these elements, schools can create more effective and equitable learning environments.

What are some of the potential unintended consequences of implementing education policies based solely on class size reduction, without considering other factors?

Policies based solely on class size reduction, inspired by studies like Project STAR, can have unintended consequences if implemented without considering the broader educational context. For example, if resources are diverted to reduce class sizes without adequately investing in teacher training or curriculum development, the overall quality of education may not improve, and outcomes could even worsen. Additionally, a uniform class size policy may not address the diverse needs of all students, potentially widening achievement gaps. A more comprehensive approach is needed to ensure that policies are effective and equitable.