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Family Dynamics

Why So Many Only Children Excel in School

The downside: Parents who may apply too much pressure.

Key points

  • Research consistently finds that only children tend to perform better academically than kids with siblings.
  • “Dilution theory” can help explain an only child’s educational advantage.
  • No matter how many children one has, reading to and with a child can be an academic equalizer.
  • Spacing between siblings could give younger ones access to equal parental resources.

The evidence has been piling up for decades in studies that compare the scholastic performance of only children and their peers with siblings: Only children of all ages appear to have a definite academic advantage.

As the population of only children rises throughout developed countries, large-scale studies of only children are possible. Much of the school-related research has been conducted in China, a country with a government-mandated, one-child policy that restricted most families to having a single child; the mandate was in place for over three decades.

One such recent study, “Differences in School Performance Between Only Children and Non-Only Children: Evidence from China,” evaluated the performance of more than 90,000 fourth graders, almost one-third of whom were only children. The study explored several questions, including: Does only child status affect math achievement, physical fitness, school feeling, and expectations of school? Overall results point to only children both performing better academically and having more positive feelings about attending school, with some differences found for girls versus boys and in urban versus rural schools.

Looking at seventh and eighth-grade participants in the study, "The Only Child, Birth Order and Educational Outcomes," the authors conclude that “the academic performance of only children is significantly better than that of children with siblings.” The researchers looked specifically at four avenues—financial resources, parenting time, the closeness of parent-child relationships, and personality traits—to determine what gives only children an educational advantage.

When comparing adolescent-only children to their peers with siblings, the plusses for onlies hold. In their own words, the authors of the study recapped, “Apparently, family size has a measurable effect on academic outcomes. A family’s overall mental maturity level, undivided resources, and heightened parental responsiveness and care may all have assisted singletons in their schooling.

In addition, the benefits of family resources on academic outcomes also promote firstborns and can be extended to laterborns but not without decrement. The decreasing benefits are shown for laterborns from medium to large families in their reported lower educational expectations, less time spent on homework, and lower grades.”

When reviewing the academic performance of only children and children with siblings in junior high school, the researchers reached a similar conclusion. They note, “Concerning academic outcomes, Chinese children without siblings appear to have higher academic achievements and cognitive abilities than children with siblings.”

Those findings were replicated in other countries as well. In her study, “Examining Sibling Configuration Effects On Young People’s Educational Aspiration and Attainment,” Feifei Bu of Essex University in England reports: “Firstborn children (whether male or female) have higher aspirations and that these aspirations play a significant role in determining later levels of attainment.”

Accounting for parents' education and professional status, Bu found that firstborns are 16 percent more likely to attend further education than their younger siblings, and firstborn children were 7 percent more likely to aspire to complete their higher education than younger siblings.

The more offspring, the more competition for parents’ time, attention, and available finances. As the family adds brothers and sisters, each child gets a smaller piece of the “pie.”

Why Only Children Do Well in School

Probably the biggest factor is resources being spread thin in larger families, as sociologist Douglas Downey describes in his “dilution theory,” echoing some of Feifei Bu’s conclusions. Years ago, Downey analyzed responses from 24,599 eighth graders in a (U.S.) National Education Longitudinal Study. He posits, and many agree, that as family size grows, parents have less time, money, and resources to invest in each child. “Parental resources explain most or all of the inverse relationship between sibship size and educational outcomes,” notes Downey. His theory has held up for decades through numerous studies in China and other countries.

In their China study cited above, Lao and Dong gave the dilution theory a slightly different spin to explain why the only child’s academic performance tends to be “better” than that of children with siblings: “This is a result of differences in parental material and nonmaterial resources, and the closeness of parent-child relationships.” That bond between only children and their parents provides “a higher grade of openness and extraversion [that] help the educational outcomes of only children.”

Openness in the parent-child relationship is a non-material resource that links positively to cognitive ability. It is certainly a resource that can be shared in homes with more than one child. Parents’ approach to or attitude toward education will also influence how well their child or children do in school. Researchers also point out that a wide age gap between siblings can free up financial and other resources for any younger siblings.

Do all only children go to the head of the class? Of course not, but these studies suggest that only children have a distinct edge. However, the educational benefits of their singleton status come at the risk of parents putting too much academic pressure on an only child, who may wind up with a negative feeling and attitude about school.

What about children in larger families? In her British research, Feifei Bu noted a clear firstborn advantage, but found “no evidence that sibship size influences either educational aspiration or attainment.”

One of the big equalizers for all children academically is having parents read to and with them starting at young ages. Researchers from the Universities of Warwick and Cambridge in the UK and Fudan University in China feel confident that reading is linked “to important developmental factors in children, improving their cognition, mental health, and brain structure, which are cornerstones for future learning and well-being.”

Copyright @2023 by Susan Newman

Facebook/LinkedIn image: NDAB Creativity/Shutterstock


Bu, Feifei. (2016). “Examining sibling configuration effects on young people’s educational aspiration and attainment.” March 15: Advances in Life Course Research: Volume: 27, p.69 -79

Chaochao Jia, Zhaoxi Yang, Tao Xin, Youfa Li, Yehui Wang and Tao Yang. (2022). “Differences in School Performance Between Only Children and Non-only Children: Evidence from China.” Frontiers in Psychology. January 13.

Downey, Douglas B. (1995). “When Bigger Is Not Better: Family Size, Parental Resources, and Children's Educational Performance.” American Sociological Review: October, pp. 746-761.

Lao, Yehui and Dong, Zhiqiang. (2019) "The only child, birth order and educational outcomes." Economics, vol. 13, no. 1, pp. 2019-28.

Yixiao Liu Quanbao Jiang(2021). “Who Benefits From Being an Only Child? A Study of Parent–Child Relationship Among Chinese Junior High School Students.” Frontiers in Psychology., 08 January8. Volume 11.

Yun-Jun Sun & Barbara J. Sahakian et al.(2023). “Early-Initiated Childhood Reading for Pleasure: Associations with Better Cognitive Performance, Mental Well-being and Brain Structure in Young Adolescence.Psychological Medicine: 28 June. DOI: 10.1017/S0033291723001381

Zeng-yin Chen, Ruth X. Liu. (2014). "Comparing Adolescent Only Children with Those Who Have Siblings on Academic Related Outcomes and Psychosocial Adjustment", Child Development Research, Article ID 578289, 10 pages, 2014.

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