The study examined the use of the Monitor by the students and tests the validity of Krashen’s Monitor model of second language acquisition theory through pre-tests and post-tests, while learning English as a second language in classroom- setting. The study was conducted in two government schools at Hamirpur, Himachal Pradesh among the students of class six and eight. The social setup of Hamirpur is such that the social environment provides very limited exposure to English. They learn English in the formal setting of classroom only. It has also been examined whether the conscious use of the monitor based on scientific understanding of the structure of English would enhance the proficiency level of students. It is found that without formal exposure, the rules (the Monitor) cannot be used. It justifies that the monitor plays a significant role only when the students are ready for its introduction. According to this study, the introduction of grammatical rules must be carefully graded. This study shows that there is a critical age at which the Monitor can play a significant role. Learning can also lead to acquisition in certain situations.