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Conceived and designed the experiments: Critical evaluation and revision of the paper: Does achievement independent of ability or previous attainment provide a purer measure of the added value of school? In a study of pairs of year-old twins in the UK, we measured achievement with year-long teacher assessments as well as tests. The pervasiveness of genetic influence in how and how much children learn is compatible with an active view of learning in which children create their own educational experiences in part on the basis of their genetic propensities.

A measure of academic achievement uncorrelated with ability or previous attainment is an appealing construct, relevant for several current controversies and goals in education [1][2][3]. A novel approach in understanding measures of added value is to assess the joint and independent contributions of nature genetics and nurture environment to added value indicators.

To be able to tease apart the effects of nature and nurture, a genetically sensitive study is needed, such as a twin or adoption study [5]. To date, these methods have been used sparingly in educational research [6]although they have been used widely in psychological and medical research with great success [7]. Twin studies provide a useful indication of the relative contributions of genetic and environmental factors on individual differences in measured traits [5][7][8][9]. The twin method uses MZ monozygotic, identical and DZ dizygotic, fraternal twin intraclass correlations to dissect phenotypic variance into genetic and environmental sources [7].

Environmental variance can be dissected into shared environmental effects i. These genetic and environmental effects are commonly known as A, C and E. Heritability can be estimated by doubling the difference between MZ and DZ twin correlations.

Shared environment C, for effects in common to family members refers to variance that makes MZ and DZ twins similar beyond twin similarity explained by additive genetic effects. C can be estimated by subtracting the estimate of heritability from the MZ correlation.

In addition, non-shared environmental influences E can be estimated from the total variance not shared by MZ twins; non-shared environmental influences are the only influences deemed to make MZ twins different. E also includes measurement error. A more elegant way of estimating the ACE parameters is maximum likelihood structural equation model fitting analysis [7][9]which provides more detailed estimates of genetic and environmental effect sizes that make assumptions explicit and provides confidence intervals for the parameter estimates.

Behavioral genetics and the twin method are concerned with the genetic and environmental influences on individual differences in complex traits. Such complex traits are the outcome of multiple genetic factors alongside and potentially in interaction with multiple environmental factors throughout development. The focus is on variation in genes and environments in relation to variation in outcomes; as such the statistics of behavioral genetics concern population or sample level effects, rather than case studies of particular individuals’ genetic and environmental profiles.

Studies specifically focusing on reading abilities show a similar pattern of results with moderate to high heritability and modest shared environmental influences [14][15].

A striking finding is that genetic influences appear to have largely generalist effects across diverse cognitive and academic abilities [18][19]. For example, the average genetic correlation an index of the degree to which nomativa influences on one trait also influence another trait between diverse cognitive and academic domains was 0.

At first 5, this high degree of genetic overlap instguo different cognitive and academic measures suggests that correcting achievement measures for general cognitive ability would remove the genetic influence on achievement.

The evaluation of schools has increased steadily since the early s, with the ultimate aim of encouraging competition and thereby driving improvements in education. The concept is straightforward: Taylor and Nguyen [21] state that:.

The current study aims to investigate whether removing ability and previous attainment from school achievement does in fact remove the genetic influence on school performance. Within the literature some studies have used cognitive abilities tests as their measure of previous attainment [3]whereas others have focused on assessments of previous school performance [22].


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For this reason, we conduct analyses using both ability i. In addition, we extend these analyses by controlling for both ability and previous achievement, which provides a strong test of any residual genetic influence on school achievement outcomes.

Analyses of the determinants of added value suggest that both school-level and pupil-level characteristics are important [4][21]. Given that the concept of added value is to assess the contribution of the school environment to students’ normztiva, it seems reasonable to predict that indices of added value will show more shared environmental influence than normatova measures of achievement, and that genetic influences inatruo be reduced.

The TEDS sample 15 been shown to be reasonably representative of the general population in terms of parental education, ethnicity and employment status [16]. For cases where zygosity was unclear from this questionnaire, DNA testing was conducted. Not all teachers provided information on National Curriculum levels and some twins did not complete all of the web tasks; exact N values for our nor,ativa of ability and achievement are presented below.

The parents of the twins provide informed written consent for each TEDS assessment. The twins’ academic performance was assessed throughout the school year by their teachers, using the assessment materials of the National Curriculum for England and Wales NCthe core academic curriculum developed by the Qualifications and Curriculum Authority QCA [26].

Teachers were contacted when the children were in the second half of their school year so that the teachers would be familiar with the children’s performance during the school year. Teachers were sent a covering letter with the background and aims of TEDS, as well as explaining that we had obtained consent from the twins’ parents to ask teachers for information about the child’s performance at school.

For the study at age 12, the NC Teacher Assessments at Key Stage 3 were used, which are designed for children aged 11—14 years old. When the twins were 12 years old, teachers assessed three nprmativa areas of achievement: Normatiav including speaking and listening; reading; and writing ; mathematics including using and applying mathematics; number and algebra; shape, space and measures; and handling data ; and science including scientific enquiry; life processes and living things; physical processes; and materials and their properties.

Teachers rate performance from levels 1 to 8.

These judgments were not made specifically for the present study, but rather form the continuing assessment of each child that ultimately leads to the final NC Teacher Assessment score unstruo to the QCA at the end of the key stage, which summarizes the child’s academic achievement during that period. Reminders of the NC criteria used to select the appropriate attainment level were provided as part of the questionnaire.

The teacher-rated achievement scales are highly correlated, with an average intercorrelation of. For this reason, we calculated a composite achievement score as a mean of the three achievement domains: English, mathematics and science. There were complete pairs of twins with this NC achievement composite; monozygotic MZ, identical pairs; and dizygotic DZ, fraternal pairs. Further details about these measures have been published previously [16][18]and further information about the UK National Curriculum is available at http: To complement our teacher ratings of school achievement we also collected test data on reading and math performance at 12 years.

We created a web-based cognitive battery to allow collection of test data from the whole TEDS sample, which is spread across the UK. We have shown that our web-based cognitive test battery is a reliable and valid method for collecting cognitive data on children as young as 10 years old [27].

For example our mathematics web battery and the equivalent paper-and pencil test correlated. Additionally, we found no correlation between internet speed i.

At 12 years we included three measures of reading achievement and three measures of mathematics achievement in our cognitive web battery. Three measures of reading ability were used at 12 years: The twins completed an adaptation of the reading comprehension subtest of the Peabody Individual Achievement Test [28]which we will refer to as PIAT rc.

The PIAT rc assesses literal comprehension of sentences. The sentences were presented individually on the computer screen. Children were required to read each sentence and were then shown four pictures.


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They had to select, using the mouse, the picture that best matched the sentence they had read. All children started with the same items, but an adaptive algorithm modified item order and test discontinuation depending on the performance of the participant. The internet-based adaptation of the PIAT rc contained the same practice items, test normatiga and instructions as the original published test.

Questions are grouped into three categories: Assessing Knowledge and Understanding e. Within each category, questions about words, sentences, and short paragraphs are asked. Because we were primarily interested in comprehension skills, we used questions from the two relevant categories, Comprehension, and Evaluation and Analysis 20 items from each category. Correct answers were summed to give a total comprehension score. This is a measure of reading speed and rate that requires the ability to read and comprehend insteuo sentences quickly e.

Low performance on reading fluency may be a function of limited basic reading skills or comprehension. There is a time limit of 3 minutes for this test. Correct answers were summed to give a total fluency score. In order to assess mathematics, we developed an internet-based battery that included questions from three different components of mathematics. The presentation of items was streamed, so that items from different categories were mixed, but the data recording and branching were done within each category.

The items were drawn from the following three categories: The mathematics battery is described in more detail elsewhere [32]. The test achievement scales were moderately correlated, with an average intercorrelation of. We calculated notmativa composite achievement score as the mean of the six achievement web measures. There were pairs of twins with this web achievement composite; MZ; and DZ.

As well as tests of achievement, we also included ability tests in our web-based cognitive battery at 12 years.

We created a general cognitive ability g score as the mean of the four tests. When we correct for previous achievement at 10 years we use the same NC teacher reports English, mathematics and science and tests reading PIAT rc and mathematics NferNelson from our year web-battery [27]. All measures were standardized to a mean of zero and a standard deviation of 1 on the basis of the entire sample of twins with children with major perinatal and medical problems excluded.

To create the ability-corrected achievement scores, both teacher ratings and test-based scores, we used a standard nornativa onto general cognitive ability, and saved the standardized residuals.

The correlations between g and achievement for teacher ratings and test data before the regression were. Thus our corrected achievement scores do not correlate with general cognitive ability. These results are highly similar to those found in research using more conventional measures; in elementary school correlations of about 0.

The same regression procedure was used to correct for previous achievement, as well as the combined effect of previous achievement instrup ability g.

Because twins are perfectly correlated for age and same-sex twins are correlated perfectly for sex, variation associated with age or sex would contribute to the correlation between twins. That is, data uncorrected for age and sex would inflate twin normwtiva. For this reason, and as is standard in twin analysis, all measures were also corrected for age and sex effects using a regression procedure [37].

Twin intraclass correlations were calculated, which index the proportion of total variance due to between-pair variance [38].

Added Value Measures in Education Show Genetic as Well as Environmental Influence

Rough estimates of genetic Ashared environmental influences C; that jnstruo twin pairs more similar to one anotherand non-shared environmental influences E; that no not contribute to similarity between twinscan be calculated from these twin correlations.

Mx software for structural equation modelling was used to perform standard twin model-fitting analyses [39]. Rather than removing the g covariance from the variance of achievement scores prior to analysis, multivariate genetic analysis considers all of the variance of achievement scores as well as all of the variance of g, and it decomposes the covariance between them into genetic and environmental components of covariance [7][40].