Amidst the backdrop of the pandemic, a profound realization swept over young kids like a gentle breeze—a newfound appreciation for the invaluable presence of an older sibling. They witnessed firsthand the blessings bestowed upon them by having a constant companion, a guiding mentor, and a steadfast pillar of support. Indeed, older siblings donned a myriad of roles in their younger counterparts’ lives—playmate, confidant, friend, and even a guardian angel when times grew tough. The realm of research has delved deep into the captivating realm of sibling dynamics, particularly exploring the phenomenon known as sibling spillover effects on educational attainment. Within this vibrant tapestry of literature, a resounding chorus emerges, heralding the remarkable influence that older siblings wield in shaping the educational journey and holistic development of their younger counterparts.

In our new study, we explore the sibling spillover effects within elementary and middle school levels, as well as the disparities between socially disadvantaged and advantaged families. To conduct this analysis, we utilize administrative data encompassing all children born between 1988 and 2004, who were enrolled in public schools in North Carolina. Our focus lies in comparing younger siblings who share similar individual and family characteristics related to academic performance, with the exception of divergent academic achievements observed in their older siblings.

Here’s what we discovered: older siblings who are born just after the school-entry cutoff date tend to be the oldest students in their classes. This means they have a little extra time before starting school, giving them an advantage in terms of their development and learning. As a result, these older siblings often perform better academically.

But here’s something fascinating: When older siblings do well in school, it actually helps their younger siblings do better too, especially when they reach middle school. And this effect is even stronger in families that face challenges. For example, we found that this positive impact is greater in non-Hispanic Black families compared to non-Hispanic White families. It’s also more pronounced in single-mother families compared to families with both parents, and for students attending schools with higher levels of poverty compared to those in schools with lower poverty levels. There are a few reasons why this happens.

First, older siblings can be role models for their younger siblings. They can inspire them to work hard and take their education seriously. When younger siblings see their older siblings doing well in school, it motivates them to do the same.

Second, positive attitudes towards education can be contagious within a family. When older siblings have a positive mindset and show enthusiasm for learning, it can rub off on their younger siblings. This creates an environment where everyone values education and strives to do their best.

Lastly, parents often make investment decisions that promote equality among their children. They want all their children to have an equal chance at success. So, when they see that an older sibling is excelling academically, they may provide extra support and resources to help the younger siblings achieve similar success.

Now let’s talk about the magnitudes of these effects we found. We found that around 23% of the test score gains of older siblings born shortly after the school-entry cutoff date actually spilled over to benefit the academic performance of their younger siblings during middle school. What’s truly remarkable is that the impact of sibling spillover we observed is comparable to about 6% of the performance gap between Black and White students in the United States. When looking at the various factors that contribute to the connection between test scores among siblings, such as genetics and shared family background, our findings suggest that sibling spillover effects account for approximately one-third of these connections.

Sixth grade marks the crucial transition between elementary to middle school, and guess what? It’s during this time that the sibling spillover effects really kick into high gear! Think about it: as students move into middle school, everything changes. New classmates, new teachers, and a whole new atmosphere. And guess who’s right there by their side, making a significant impact? Their older siblings! This transition period turns out to be a goldmine for sibling influence. The effects of older siblings on their younger counterparts’ academic performance reach their peak during this time. It’s like a power surge of support and inspiration flowing from the older sibling to their younger sibling, propelling them forward.

What all these findings mean? The positive effects of older siblings on their younger counterparts during middle school can have long-term implications for their future success. Disadvantaged families, who often face economic hardships, may experience negative effects that spill over from older to younger siblings. To address this, it is crucial to provide robust support systems for disadvantaged families in the United States, ensuring they have access to necessary resources.

However, there is also a silver lining. When parents and society invest in the educational attainment of the older sibling, it can have a positive ripple effect on the academic performance of the younger sibling. This means that efforts to support and enhance the education of older siblings can indirectly benefit their younger siblings, especially in Black families, single-parent households, and low-income families. By recognizing and investing in these opportunities, we can promote educational equity and empower families to break the cycle of disadvantage.

Emma Zang, Ph.D., is assistant professor of sociology, biostatistics, and global affairs at Yale University. Her research interests lie at the intersection of health and aging, family demography, and inequality. She is also interested in developing and evaluating statistical methods to model trajectories and life transitions. Her research has been covered by major media outlets in the United States, China, South Korea, India, and Singapore, such as CNN, NBC, the Washington Post, the Boston Globe, Harvard Business Review, ThePaper.cn (China), and the Straits Times (Singapore). Twitter: @DrEmmaZang.