<![CDATA[The mother tongue remains an important part of elementary school students’ daily communication, especially in communities where local languages are actively used at home and in social interaction. This study aims to describe patterns of mother tongue use and explain their relationship with Indonesian language proficiency among third-grade students at SD Negeri 7 Mawasangka Tengah. A descriptive qualitative approach was employed. Data were collected through observation, interviews, and documentation, with credibility ensured through source and method triangulation. The findings show that the mother tongue dominates informal communication at school and at home, while Indonesian is used more frequently in classroom learning and formal situations. The mother tongue helps students understand teachers’ explanations, communicate more comfortably, and maintain connections with local culture. However, some students still experience difficulties with Indonesian vocabulary, complex instructions, and expressing ideas in complete sentences. Code-mixing also occurs when students cannot find appropriate Indonesian words. These findings indicate that the mother tongue can function as a linguistic bridge in learning Indonesian. Teachers should therefore use it proportionally while expanding students’ opportunities to use Indonesian in academic contexts. Keywords: mother tongue; Indonesian language; elementary school students; code-mixing; language learning]]>
