Learning mathematics with shackles: How lower reading comprehension in the language of mathematics instruction accounts for lower mathematics achievement in speakers of different home languages.

Achievement in mathematics has been shown to partially depend on verbal skills. In multilingual educational settings, varying language proficiencies might therefore contribute to differences in mathematics achievement. We explored the relationship between mathematics achievement and language competency in terms of home language and instruction language proficiency in the highly multilingual society of Luxembourg. We focussed on third graders' linguistic and mathematical achievement and used data from the national school monitoring program from two consecutive years to assess the influence of children's language profiles on reading comprehension in German (the instruction language) and mathematics performance. Results were similar for both cohorts. Regression analysis indicated that German reading comprehension was a significant predictor of mathematics achievement when accounting for both home language group and socioeconomic status. Moreover, mediation analysis showed that lower mathematics achievement of students with a home language that is very different from the instruction language relative to the Luxembourgish reference group were significantly mediated by achievement in German reading comprehension. These findings show that differences in mathematics achievement between speakers of a home language that is similar to the instruction language and speakers of distant home languages can be explained by their underachievement in reading comprehension in the instruction language. Possible explanations for varying performance patterns between language groups and solutions are being discussed.