The concept of explained proportion of variance or modeled proportion of variance is reviewed in the situation of the random effects hierarchical two-level model. It is argued that the proportional reduction in (estimated) variance components is not an attractive parameter to represent the joint importance of the explanatory (independent) variables for modeling the dependent variable. It is preferable instead to work with the proportional reduction in mean squared prediction error for predicting individual values (for the modeled variance at level 1) and the proportional reduction in mean squared prediction error for predicting group averages (for the modeled variance at level 2). It is shown that when predictors are added, the proportion of modeled variance defined in this way cannot go down in the population if the model is correctly specified, but can go down in a sample; the latter situation then points to the possibility of misspecification. This provides a diagnostic means for identifying misspecification.

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This study is the first to systematically review and quantify the effects of physical activity on brain structure and neurophysiological functioning in children. Electronic data bases were searched for relevant studies. Studies that met the following criteria were included: (1) used an RCT or cross-over design, (2) examined the effects of physical activity on brain structure and/or neurophysiological functioning, (3) included children (5–12 years old) (4) included a control group (RCTs) or control condition (cross-over trials). A total of 26 and 20 studies were included in the systematic review and meta-analysis, respectively, representing and accompanying 973 and 782 unique children. Main analyses were separated for short-term and long-term physical activity and for effects on brain structure and neurophysiological functioning with a distinction between children from healthy and clinical populations. We found evidence for significant beneficial effects of long-term physical activity on neurophysiological functioning ( d = 0.39, p < 0.001). In addition, short-term physical activity may induce changes in neurophysiological functioning ( d = 0.32, p = 0.044), although this evidence showed limited robustness. No meta-analytic evidence was found for positive effects on brain structure. The results underline the importance of physical activity for brain development in children.

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Critical reviews from ``outside'', notably educational sociologists arguing mainly from a British context, have caused some ripples, and maybe even waves, among school effectiveness researchers. To a large extent these external criticisms and the overall nature of the response from school effectiveness researchers are neatly summarized in the following quote from Townsend: ``be like us'', say the critics, and the answer is ``no thanks''. In this article the arguments form the ``external'' critics and the response from school effectiveness researchers will not be repeated. Some of the topics in the debate will be revisited, however. The ®rst one is the discussion with respect to the impact of ``contextual'' or composition effects concerning the average socioeconomic background of students in schools and classrooms. This is one area, that bears upon the foundations of the school effectiveness concept, although it is not, as the critics would have it, a neglected area. The second one concerns conceptualization and theoretical explanation of school effectiveness, as the debate may not have been suf®ciently explicit on this issue. The rest of the paper deals with ``foundational'' issues in school effectiveness research that have not been settled decisively and with changes in perspectives on learning and instruction and educational technology that provide serious challenges. On these issues there is reason for self-criticism and realism in the way school effectiveness research can make progress.

Methods are presented for comparing grades obtained in a situation where students can choose between different subjects. It must be expected that the comparison between the grades is complicated by the interaction between the students' pattern and level of proficiency on one hand, and the choice of the subjects on the other hand. Three methods based on item response theory (IRT) for the estimation of proficiency measures that are comparable over students and subjects are discussed: a method based on a model with a unidimensional representation of proficiency, a method based on a model with a multidimensional representation of proficiency, and a method based on a multidimensional representation of proficiency where the stochastic nature of the choice of examination subjects is explicitly modeled. The methods are compared using the data from the Central Examinations in Secondary Education in the Netherlands. The results show that the unidimensional IRT model produces unrealistic results, which do not appear when using the two multidimensional IRT models. Further, it is shown that both the multidimensional models produce acceptable model fit. However, the model that explicitly takes the choice process into account produces the best model fit.

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This study is aimed at describing profiles of interpersonal behavior of Indonesian mathematics teachers and examining associations between students' perceptions of their mathematics teachers' interpersonal behavior and their motivation in learning mathematics. Data were collected with the Indonesian version of the Questionnaire on Teacher Interaction (QTI) and the Questionnaire on Motivational Dimensions. The framework of this study is based on the Model of Interpersonal Behavior that maps teachers' conduct in terms of 2 dimensions: Influence (Dominance-Submission) and Proximity (Cooperation-Opposition). A total of 506 students (grades 7 to 9) from 16 classes in 5 public secondary schools in the West Java and Jambi provinces, Indonesia, participated in the study. Data analyses were conducted including descriptive, correlational, and multilevel analyses. Results from the data analyses showed that the reliability and (validity) of the Indonesian QTI were good; teachers' ratings of their interpersonal behavior were moderate in class perceptions but (were) quite high in teachers' self-perception in both the Proximity and Influence dimensions and that associations existed between the 2 dimensions of interpersonal behavior and student motivation in learning mathematics. There was an indication that Indonesian mathematics teachers were generally perceived as directive. Implications of the findings were discussed.