Communicative competence is the goal of a language classroom (Brown, 2007). The success in learning English is sometimes indicated by the students' communication skill. Success is measured in term of the ability to carry out conversation in the target language. Furthermore, one of the objectives in foreign language teaching in Indonesia is to enhance speaking skill fluently and accurately. Basic Interpersonal Ccommunicative Skill (BICS) is a basic skill to communicate English with other people such as conversational and transactional activities. Thus, the implementation of BICS in the classroom is in line with the objective of foreign language teaching in Indonesia and the main goal of English learning in junior high school in which targets the students' ability at functional level so that the students will be fluent in English communication. The objective of this qualitative case study is to describe the implementation of BICS in in the classroom and Boarding School and the outputs of the implementation of BICS at SMP Unggulan Bilingual Boarding School (BBS) Zainul Hasan Genggong Probolinggo. To reach such an aim, the researcher collected the data by direct observation, in-depth interviewing and document review. In addition, the researcher analyzed the collected data by using three major phases of the data analysis: data reduction, data display, then drawing conclusion and verification. From the data analysis the researcher found some conclussion on the implementation of BICS is affected by some aspects. The first is classroom environment and dormitory which have been set to an English-speaking area and supported with some facilities such as smart TV, internet, and laptop. This gives opportunities to the students to their English exposure and use English as lingua franca. In addition, the implementation of BICS in this school is incorporated with every school element such the founder, the headmaster, the teachers, the students, the staffs and parents. It is impossible for the school to run the whole ideas relying on a single element of the school. And the last, the immersion program and sheltered mode method applied in this school. The immersion method has been conditioned in the form of sheltered mode which is the students absorb the EFL in conditioned environment and forced them into additive bilingualism that is the students with their own native language are able to communicate with high proficiency in EFL mode, but in some cases, by the students on the lesser language proficiency found that: subtractive bilingualism, Semilingualism and Monolingualism (Lambert, 1974).