“Big-fish-little-pond” is a concept well known among education professionals: As the theory goes, students in higher-achieving schools will compare themselves with their peers and consider themselves less capable, while equally performing students in lower-achieving settings have more confidence.

The effect appears in all subjects, from math to science to history, and at all levels of education. Low-income and high-income students exhibit it. Countries all around the world see it.

While the phenomenon has been observed in many studies over the years, no large-scale, cross-national analysis credibly showed causation. There was always the possibility, then, that another factor, such as an unobserved trait of individual students or their parents, explained why students in high-performing schools exhibited more self-doubt.

Now, a team of researchers led by Prashant Loyalka, an assistant professor at Stanford Graduate School of Education, has found a direct link between highly competitive programs and students’ negative self-concepts. In a study published in the November 2018 issue of Comparative Education Review, they provide the strongest evidence yet that the big-fish-little-pond effect exists.

Moreover, Loyalka’s analysis reaffirms what previous studies suggested: The phenomenon affects girls and boys equally and across all countries — wealthy or poor, big or small.

“This study tells us, in a meaningful way, what education psychologists have long suspected,” Loyalka said. “As humans, we have a tendency to compare ourselves to others in terms of our abilities and, because of that, we tend to feel better or worse about ourselves. It is fundamental to who we are.”

Causation matters

The concept of the big-fish-little-pond effect dates to the mid-1980s. The theory refers to how students think of themselves as learners, or their “academic self-concept.” Researchers have observed that when you are a “big fish” (high-achieving student) in a “little pond” (lower-achieving school), you have more positive academic self-concept. Conversely, when equally talented students (little fish) are in high-achieving environments (big pond), they compare themselves to their peers and conclude they don’t measure up.

Academic self-concept is important to student outcomes. Research has shown that it affects how well students do in school, their attitudes about the classroom and their placement in more advanced programs. 

The theory made so much sense and scholars found such consistent correlations across countries, subjects, genders and income levels that it was treated as established fact. A few small studies showed causation, but none attempted to do so in a generalizable way.

“Everybody just agreed that the effect existed,” said Loyalka, who is also a fellow at Stanford’s Freeman Spogli Institute for International Studies.

But showing causation in education research is especially critical as policymakers, school administrators, teachers and parents grapple with decisions about how best to allocate money to programs, improve teaching, and identify schools that are the right fit.