The purpose of this interpretive research was to identify and clarify the impacts deriving from the promotion of communication skills in a multicultural classroom using Genetic Instructional Units (GIUs), which are based on the social constructivist approach. Vygotskian notions of classroom practices which promote effective communication in concept development were a key design element in the development of the GIUs. These developed GIUs were implemented with 8 Grade 12 disadvantaged students, who were of different minority groups including 1 Yao, 1 Leesor, 5 Mong students; and 1 prostitute-at-risk student. Data from the students’ journals, the teacher’s journal, videotape recordings, cassette tape recordings, and observation forms were analyzed. The GIUs included instructional materials, teaching manuals, and students’ workbooks which were implemented in the classroom. The findings showed that using understandable activities, practical instructional materials, grouping students in small mixed ability cooperative groupings and cross-sex and mixed ability pairings, periodic dynamic assessment, and studying the limitations of the students’ communication skills could promote the students’ communication skills. The results could be used to conclude that GIUs help to enhance the communication skills of disadvantaged students.