Impact of family language and testing language on reading performance in a bilingual educational context

Background: When different languages co-exist in one area, or when one person speaks more than one language, the impact of language on psychological and educational assessment processes can be considerable. The aim of this work was to study the impact of testing language in a community with two official languages: Spanish and Basque. Method: By taking the PISA 2009 Reading Comprehension Test as,a basis for analysis, four linguistic groups were defined according to the language spoken at home and the test language. Psychometric equivalence between test forms and differences in results among the four language groups were analyzed. The comparison of competence means took into account the effects of the index of socioeconomic and cultural status (ISEC) and gender. Results: One reading unit with differential item functioning was detected. The reading competence means were considerably higher in the monolingual Spanish-Spanish group. No differences were found between the language groups based on family language when the test was conducted in Basque. Conclusions: The study illustrates the importance of taking into account psychometric, linguistic and sociolinguistic factors in linguistically diverse assessment contexts.