When do children become unequal in reading and math skills? Some research claims that inequality grows mainly before school begins. Some research claims that schools cause inequality to grow. And some research-including the 2004 study ''Are Schools the Great Equalizer?''-claims that inequality grows mainly during summer vacations. Unfortunately, the test scores used in the Great Equalizer study suffered from a measurement artifact that exaggerated estimates of inequality growth. In addition, the Great Equalizer study is dated and its participants are no longer school-aged. In this article, we replicate the Great Equalizer study using better test scores in both the original data and a newer cohort of children. When we use the new test scores, we find that variance is substantial at the start of kindergarten and does not grow but actually shrinks over the next two to three years. This finding, which was not evident in the original Great Equalizer study, implicates the years before kindergarten as the primary source of inequality in elementary reading and math. Total score variance grows during most summers and shrinks during most school years, suggesting that schools reduce inequality overall. Changes in inequality are small after kindergarten and do not replicate consistently across grades, subjects, or cohorts. That said, socioeconomic gaps tend to shrink during the school year and grow during the summer, while the black-white gap tends to follow the opposite pattern.

Objective: To assess the relative importance of school and nonschool risk factors, this study estimated whether overweight and obesity prevalence grows faster during the school year or during summer vacation. Methods: In the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11, a nationally representative complex random sample of 18,170 U.S. children was followed from the fall of kindergarten in 2010 through the spring of second grade in 2013. Children's weight and heights were measured in schools each fall and spring. A multilevel growth model was used to estimate growth in mean BMI, overweight prevalence, and obesity prevalence during each summer and each school year. Results: From the fall of kindergarten to the spring of second grade, the prevalence of obesity increased from 8.9% to 11.5%, and the prevalence of overweight increased from 23.3% to 28.7%. All of the increase in prevalence occurred during the two summer vacations; no increase occurred during any of the three school years. Conclusions: The risk of obesity is higher when children are out of school than when they are in school.

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It is suggested that a low‐frequency ‘gradient drift’ instability may be important for the formation of striations in barium ion clouds released in the ionosphere above the E layer. The theory predicts that the trailing edge (with respect to the neutrals) of the plasma cloud will be unstable while the leading edge is stable, in qualitative agreement with observations. The growth time is relatively independent of wavelength and is of order d/Uo, where d is the typical density gradient length and Uo is the velocity of the cloud with respect to neutrals. Predicted growth times varying from seconds in the auroral zone at high latitude to minutes at midlatitudes are also in agreement with observation. Wavelengths of waves with zero phase velocity are found to be given approximately by λ = 2πd, which can be verified by optical observations.

One of the most consistent patterns in the social sciences is the relationship between sibship size and educational outcomes: those with fewer siblings outperform those with many. The resource dilution (RD) model emphasizes the increasing division of parental resources within the nuclear family as the number of children grows, yet it fails to account for instances when the relationship between sibship size and education is often weak or even positive. To reconcile, we introduce a conditional resource dilution (CRD) model to acknowledge that nonparental investments might aid in children's development and condition the effect of siblings. We revisit the General Social Surveys (1972-2010) and find support for a CRD approach: the relationship between sibship size and educational attainment has declined during the first half of the twentieth century, and this relationship varies across religious groups. Findings suggest that state and community resources can offset the impact of resource dilution-a more sociological interpretation of sibship size patterns than that of the traditional RD model.