The aim of this study was to develop a deep understanding of interaction in language classroom in foreign language context. Interviews, as major instrument, to twenty experienced English language teachers from eight lower secondary schools (SMP) were conducted in Jakarta, completed by focus group discussions and class observation/recordings. The gathered data was analyzed according to systematic design of grounded theory analysis method through 3-phase coding. A model of classroom interaction was formulated defining several dimensions in interaction. Classroom interaction can be more comprehended under the background of interrelated factors: interaction practices, teacher and student factors, learning objectives, materials, classroom contexts, and outer contexts surrounding the interaction practices. The developed model of interaction for language classroom is notably to give deep descriptions on how interaction substantially occurs and what factors affect it in foreign language classrooms at lower secondary schools from teachers' perspectives.