The blended learning approach utilizes modern technologies and electronic media in teaching to create a technology-based environment. However, it is not an exclusive online environment because the teacher and the students have to be present in a traditional face-to-face classroom. It is widely believed that adopting a blended learning approach will enable learners to have quality educational opportunities and improve their performance. The incentive for conducting the research is to evaluate the effect of the blended learning approach on high school students' English proficiency. Specifically, the study aimed at answering the question: is there a significant difference in the Twelfth-Grade students' English language proficiency as measured by IELTS due to the model of delivery (Blended learning model and the traditional delivery model)? To achieve the study's goal, the researcher applied the experimental method and used IELTS to measure language proficiency. The study sample selected purposively consisted of 63 male twelfth-grade students in one of the private schools in Al Ain, United Arab Emirates (UAE). The study sample was assigned to two groups: the experimental group taught using blended learning consisted of 31 students, and the control group led by the traditional method consisted of 32 students. The results showed statistically significant differences at the level of (a<0.01) between the means of the results of the two groups on the post achievement test in favor of the experimental group. These results illustrated the impact of adopting the blended learning approach in an English Foreign Language (EFL) setting on students' achievement in standardized tests. However, the successful implementation of blended learning largely depends on how responsible and committed students are towards active learning.