The use of eligibility for a free lunch as a measure of a student's socioeconomic status continues to be a fixture of quantitative education research. Despite its popularity, it is unclear that education researchers are familiar with what student eligibility for a free lunch does (and does not) represent. The authors examine the National School Lunch Program, which is responsible for certifying students as eligible for a free lunch, and conclude that free lunch eligibility is a poor measure of socioeconomic status, which suffers from important deficiencies that can bias inferences. A table characterizing key strengths and weaknesses of variables used as measures of socioeconomic status is provided to facilitate comparisons.

Manifestations of internalizing problems, such as specific symptoms of anxiety and depression, can change across development, even if individuals show strong continuity in rank-order levels of internalizing problems. This illustrates the concept of heterotypic continuity, and raises the question of whether common measures might be construct-valid for one age but not another. This study examines mean-level changes in internalizing problems across a long span of development at the same time as accounting for heterotypic continuity by using age-appropriate, changing measures. Internalizing problems from age 14-24 were studied longitudinally in a community sample (N = 585), using Achenbach's Youth Self-Report (YSR) and Young Adult Self-Report (YASR). Heterotypic continuity was evaluated with an item response theory (IRT) approach to vertical scaling, linking different measures over time to be on the same scale, as well as with a Thurstone scaling approach. With vertical scaling, internalizing problems peaked in mid-to-late adolescence and showed a group-level decrease from adolescence to early adulthood, a change that would not have been seen with the approach of using only age-common items. Individuals' trajectories were sometimes different than would have been seen with the common-items approach. Findings support the importance of considering heterotypic continuity when examining development and vertical scaling to account for heterotypic continuity with changing measures. (PsycINFO Database Record

Poorer language ability has been shown to predict the development of externalizing behavior problems such as aggression and conduct problems. However, the developmental process that links poorer language ability to externalizing problems is unclear. The present study examined (a) whether withinchild changes in language ability predict within-child changes in externalizing problems, (b) whether social skills are a potential mechanism that explains the association between language ability and externalizing problems, and (c) whether there are sex-related differences in the association between language ability and externalizing problems. The present study examined these questions in children (N ϭ 1,364) followed annually from 4 to 10 years of age. Language ability was assessed by a measure of receptive language (i.e., vocabulary). Externalizing problems were rated by mothers and teachers. Social skills were rated by mothers, fathers, and teachers. Findings showed that within-child changes in language ability predicted within-child changes in externalizing problems, even controlling for the family's income-to-needs ratio. We found that social skills partially mediated the association between poorer language ability and later externalizing problems, but this was limited to a between-person effect. There was not strong evidence of sex-related differences in the association. Findings suggest that language ability may play a role in the development of externalizing problems for boys and girls, and that social skills may be a mechanism that partially explains how poorer language ability leads to the development of externalizing problems. Or, alternatively, language ability, social skills, and externalizing problems may partially share common causes. Educational Impact and Implications StatementPoorer language ability in children has been shown to predict the development of externalizing behavior problems such as aggression and conduct problems, but the reasons for this are not known. In a sample of 4-to 10-year-old children, language ability predicted their changes in externalizing problems. Poorer social skills partially explained why children with poorer language ability tended to develop more externalizing problems. The association between poorer language ability and more externalizing problems was similar for boys and girls. Findings suggest that poorer language ability may play a role in the development of externalizing problems for boys and girls, and that poorer social skills may be a mechanism that partially explains how poorer language ability leads to the development of externalizing problems. However, it is also possible that language ability, social skills, and externalizing problems partially share common causes.

Many psychological constructs show heterotypic continuity-their behavioral manifestations change with development but their meaning remains the same (e.g., externalizing problems). However, research has paid little attention to how to account for heterotypic continuity. Conceptual and methodological challenges of heterotypic continuity may prevent researchers from examining lengthy developmental spans. Developmental theory requires that measurement accommodate changes in manifestation of constructs. Simulation and empirical work demonstrate that failure to account for heterotypic continuity when collecting or analyzing longitudinal data results in faulty developmental inferences. Accounting for heterotypic continuity may require using different measures across time with approaches that link measures on a comparable scale. Creating a developmental scale (i.e., developmental scaling) is recommended to link measures across time and account for heterotypic continuity, which is crucial in understanding development across the lifespan. The current synthesized review defines heterotypic continuity, describes how to identify it, and presents solutions to account for it. We note challenges of addressing heterotypic continuity, and propose steps in leveraging opportunities it creates to advance empirical study of development.