School education in Pakistan has allocated resources to upsurge English language learners (ELLs) academic achievement. But in spite of concerted efforts, students of English language specifically at elementary level continue to lag behind in their academic achievement. Additionally, English language teachers feel themselves unequipped to fulfill the linguistics and academic needs of these learners without relevant professional development training. The main objective of this quasi experimental pre-test post-test design study, therefore, was to analyze the effect of SIOP model on students’ achievement in English in comparison with students who were not taught using this model. All the students enrolled in grade 8th in elementary schools of district Lodhran served as study population. Two intact/pre-existing sections of grade 8th in two elementary schools were taken as study sample. One section with 32 students (experimental group) was taught using SIOP model while the other section with 40 students (control group) received instruction with conventional methods. The inferential analysis of pre-test post-test data exhibited statistically significant differences in experimental group students’ English achievement level who received instruction with SIOP. Findings of this study suggest that the use of SIOP model has positive effect on English language learners (ELLs) academic achievement as well as closing the English achievement gap. Finally, this study provides valuable implications for teachers, school administrators and policy makers to improve academic performance of English language learners.