In 2014, E. Pahlke, J. S. Hyde, and C. M. Allison published a meta-analysis in "Psychological Bulletin" comparing achievement and attitudes in single-sex versus coeducational schools that included 1.6 million students in grades K-12. The study concluded that "there is little evidence of an advantage of SS schooling for girls or boys for any of the outcomes." In a 2015 review of this study, however Cornelius Riordan observed that the authors "employ a 0.2 effect-size threshold in drawing these conclusions about there being no advantage to single-sex schooling. Despite the above conclusion, the research found that, in a separate analysis of just the best studies (well controlled) conducted in America, the effect size in mathematics was 0.14 for both boys and girls. The verbal performance was 0.22 for girls and 0.13 for boys... Educational research has shown that a standard effect size of 0.10 on gains from sophomore to senior year of high school is equivalent to one full year of learning by the average public school student in the United States." Thus, he says, that "Applying this standard, a difference of 0.10 (or greater) between students in single-sex and in coeducational schools would be substantially important." The analysis of the 21 other countries yielded much smaller effects, such as a 0.10 effect on mathematics for girls and a 0.06 effect for boys, and for science (0.06 for girls and 0.04 for boys). Most of the international effects, then, would fall within Riordan's stricter criterion for statistical significance.