Impact of Teacher-Initiated Code-Switching on Iranian 7th Grade EFL Students’ Spoken Accuracy and Fluency

Globalization and the increasing linguistic diversity of classrooms have challenged traditional monolingual approaches to language teaching. In EFL contexts such as Iran—where exposure to English is largely restricted to the classroom—teachers often seek innovative strategies to enhance comprehension and communication. One such approach is code-switching. This study investigated the impact of teacher-initiated code-switching on the spoken grammatical accuracy and fluency of Iranian seventh-grade EFL learners. Employing an explanatory sequential mixed-methods design, the present study consisted of a quantitative quasi-experimental phase (twelve-week intervention) followed by qualitative interviews. For the quantitative phase, the researchers selected 24 students and divided them into two groups: an experimental group and a control group. The experimental group received instruction in which the teacher purposefully switched to Persian for explanations to scaffold comprehension and reduce anxiety, whereas the control group was taught exclusively in English. Quantitative data were collected from pre- and post-tests using adapted IELTS Speaking Band Descriptors. Content validity was assessed through expert review, and inter-rater reliability was confirmed by two independent raters with adjudication of discrepancies. The results revealed that students exposed to strategic code-switching significantly outperformed their peers in both fluency and accuracy. The qualitative interviews confirmed that both students and the teacher viewed code-switching as an effective means to bridge linguistic gaps and enhance classroom communication. These findings support balanced bilingual pedagogies that strategically integrate the L1 for comprehension without diminishing L2 immersion. They offer practical implications for classroom instruction and curriculum design in EFL settings.