To determine the effectiveness of a peer tutorial strategy in the school achievement of English to high school students, whose mother tongue is not English, we made a comparison of two groups; in one, peer tutoring was carried out through the support of high average students and compared with the results of a group that did not receive the intervention. The tutors were 121 students who scored higher than 80 points in the initial exam and accepted to participate in the program. The group of tutees was formed by those who obtained scores lower than 65 and accepted to be tutored (101 formed the experimental group and 112 the control group). The peer tutoring was done in the classroom with the monitoring of the teacher, lasted 11 weeks, and focused on taking class notes and comparing them, giving feedback and clarifying doubts for 30 minutes after the teacher's explanation. The results of the midterm exam and final exam were analyzed through the Student's t-test, showing significant differences in the group that was tutored compared to the low-performing students who did not receive the intervention. The procedure was effective, finding that the use of peer support can improve school performance. It is necessary to monitor the profile of the tutors and systematize the tutorial strategy.