Predicting Academic Performance: Correlating IELTS Scores with End-of-Term Grades in Vietnamese High School Students

English proficiency is increasingly crucial in Vietnam’s globalized landscape, with standardized tests like IELTS serving as key indicators of language ability. However, effectively translating international test scores to local grading systems remains a challenge. This study aimed to establish a reliable conversion method between IELTS scores and end-of-term grades for high school students in Vung Tau, Vietnam. Utilizing a quantitative, correlational design, we analyzed data from 371 students in grade 10 at Le Quy Don specialized school. Data sources included mock IELTS scores administered by The Forum and official end-of-term grades. Pearson correlation and linear regression analyses were employed to examine the relationship between the variables. A significant positive correlation (r =0.432,p < 0.01) was found between IELTS scores and end-of-term grades. Linear regression analysis yielded a statistically significant model (End-of-term grade = 0.501 × IELTS + 5.843) for predicting grades based on IELTS scores. A conversion table was developed to provide a practical reference for educators. This study provides a valuable tool for bridging the gap between IELTS scores and academic performance in a Vietnamese educational context. The conversion table can inform educational decision-making regarding student placement, targeted support, and curriculum development, ultimately enhancing the understanding of English proficiency expectations for students and educators alike.