After models with good convergence (convergence t-ratios less than .10, reasonable standard errors; Ripley et al., 2012) were estimated for each school, parameters were pooled across individual school models using meta-analysis (Cochran, 1954; Ripley et al., 2012; Snijders & Baerveldt, 2003), which also provides information on effect variation across schools. The meta-analysis assumes that the 12 schools come from the same population. Statistical significance for population means was inferred using the normal distribution-based t-test described by Snijders and Baerveldt (2003).
