This chapter summarizes the complex nature of bilingual academic communication, highlighting the gradual and non-binary process of language acquisition. It emphasizes the importance of academic language, which is structured with regular patterns that facilitate learning in subjects like math, history, and science. It advocates for a deeper understanding of how academic language proficiency is developed through the systematic practice of lexis, syntax, and discourse.

In an era of globalization, multilingualism is vital for social mobility and equity. Educational institutions must adapt to the multilingual reality of today’s classrooms, where proficiency in a global language can open doors to social rights and international participation. The chapter stresses that multilingualism should be seen as an asset, not a transitional quirk, and highlights the benefits of bilingual education in fostering cognitive flexibility and critical thinking. Finally, it explores the need for proper resources, including qualified bilingual teachers, to make bilingual education effective and accessible to all students.

This chapter uncovers the power of academic language in bilingual education. Unlike casual speech, academic language is structured, dense, and cognitively demanding – challenging L2 learners. Success requires ‘L2 instructional competence’, blending language proficiency with advanced cognitive functions.

We explore key theories like the threshold hypothesis, which suggests a minimum language level for learning, and the interdependence hypothesis, which highlights skill transfer between languages. Classroom models categorize tasks by cognitive demand, illustrating structured speaking patterns and the need for rediscursification – language adjustments that enhance comprehension.

Academic language is crucial for professional and societal success, from writing essays to understanding abstract concepts. Biliteracy is a continuous process, supported by bilingual programmes such as CLIL and EMI. By linking cognitive insights with multilingual education, this chapter sets the foundation for quality bilingual instruction in a multilingual world.

This chapter presents argument-based validation research to evaluate the interpretation of scores from an English collocational ability test. The argument-based validity framework guided the development of an interpretation/use argument that helped identify the types and amount of research needed to evaluate the plausibility of the claims about test score interpretation. Research presented in this chapter focuses on the explanation inference which is made when test users interpret the score as having substantive meaning about the construct assessed, specifically the construct of collocational ability in academic writing. The construct was defined by specifying the nature and scope of the construct following an interactionalist construct, which consists of three parts 1) the knowledge skills and abilities of a trait, 2) the types of contexts that delimit the scope of applicability of the trait, and 3) the metacognitive strategies to put the trait into use in those contexts. The target collocation was identified and defined based on applied linguistics theory and research, analysis of test-takers‘ responses to items on the test and statistical analysis of test scores. The relationship between collocational ability and other constructs of language ability were hypothesized in the nomological network to provide a basis for interpreting observed statistical relationships among sets of test scores reflecting those constructs. Evidence from screen capturing analysis, responses on a post-test survey and post-test interviews provided backing of strategy use. Data were collected in two phases of an embedded, sequential explanatory design to first obtain results from qualitative analysis of test takers' responses and then explain the results of the quantitative data with results from the supplementary qualitative data. Evidence collected in this study supported the construct of collocational ability underlying the explanation inference and demonstrated how argument-based validity can be used to lay a foundation for interpretation of test scores that is essential to score meaning.