THE ADVANTAGES OF JOINTLY CONSIDERING FIRST AND SECOND LANGUAGE 1 The Advantages of Jointly Considering First and Second Language Vocabulary Skills Among Emergent Bilingual Children May-Britt Monsrud 1 , Veslemøy Rydland 2 , Esther Geva 3 , Anne-Cathrine Thurmann-Moe 4 and Solveig Halaas Lyster 5 Keywords: conceptual score, assessment, language proficiency, receptive and expressive vocabularies A large body of research demonstrates that many bilingual students struggle with gaining command of vocabulary at the same level as that of their monolingual peers in school language (e.g, Farnia & Geva, 2011). It is a well-established observation that insufficient vocabulary skills constitute a bottleneck for reading comprehension and ultimately for academic achievement (e.g., August & Shanahan, 2008). At the same time, bilingual children may learn different concepts and words in their L1 then in their L2, which is not taken into account when their vocabulary proficiency is only assessed in one language. Thus, there is a great need for more knowledge about typical bilingual children’s vocabulary and the best ways of investigating the semantic knowledge that bilingual children possess across their L1 (the home language) and L2 (the societal language) (Cummins, 2000; Kohnert, 2013; Paradis, 2016; Peña, Bedore, & Kester, 2016). Most studies today have focused on Spanish-English bilinguals, and less is known about vocabulary development among bilinguals in a European 1 Statped-Center for Special Needs Education, Norway, Department of Special Needs Education, University of Oslo, Metropolitan University, Faculty of Education and International Studies, Oslo, Norway 2 Department of Education, University of Oslo, Norway 3 Applied Psychology and Human Development, University of Toronto, Canada 4 Statped-Center for Special Needs, Norway 5 Department of Special Needs Education