Research has shown that the LARGER the family, the LOWER the children's achievement on test scores and grades.
Chinhui Juhn, Yona Rubinstein, and C. Andrew Zuppann, the three conomists behind this study, used the data from the US National Longitudinal Survey of Youth 1979 to assess their hypothesis.
What they discovered did confirm their theory. Each additional child resulted in less time for the others, resulting in lower scores on reading and math tests and more behavioral issues, such as anxiety, dependence, hyperactivity, and social problems.
It is then concluded that as families grow, kids suffer. Due to less parental investment, kids’ cognitive abilities decrease and behavioral issues arise. The sad thing is, the impact lasts for a very long time.