Spatial and temporal factors in the bilingual classroom that can be manipulated to maximize the bilingualism of Spanish-speaking elementary school children (that is, to minimize their lexical code switching) are presented in terms of models. The advantages and disadvantages of the dual language teaching model are compared to those of two variations on that model. Homogeneous and heterogeneous seating arrangements are contrasted, and the physical grouping of materials and location of teaching aids such as bulletin boards are discussed. The importance of teacher-student communication during transition times (such as the period between lessons and the preparation for recess) for fostering bilingualism is emphasized, and two checklists are provided for assessing student and teacher language use at these and other times. (JB)