Abstract: | Language education has often been conducted based on monoglossic ideologies that keep L1 and L2 separate, a practice that receives growing criticism as out of sync with today’s multilingual globalized world. Informed by interdependence hypotheses and translanguaging theory, this research study explored the effects of a pluri-centric approach to learning L1 and L2 simultaneously. Through a bilingual intervention course with data collected from interviews, parents’ logbooks, observation field notes, questionnaires, and L1 and L2 reading and writing tests, this case study (n = 9) revealed that the approach effectively improved learners’ L1 and L2 proficiency, learning behaviour outside the classroom, self-efficacy, and confidence. Overall, the participants also perceived the bilingual course as effective, efficient, and innovative. The study provides a basis to reflect upon transferrable skills and core underlying proficiency as powerful concepts to draw upon in enhancing bilingual proficiency and effecting positive changes in learners’ behaviour and psychological well-being. |