Beginning with a consideration of some commonsense and professional conceptions of what a formal situation might comprise, this paper goes on to ask the question: where along a linear array which has its poles in exemplars of formal and informal speech-exchange systems, can classroom talk be placed? Its answer is given in part in the form of rules for the taking of turns in classrooms, these being modifications of those, already established in the literature, for natural conversation. These rules allow for and require that formal classroom situations be constructed so as to involve differential participation rights for parties to the talk depending on their membership of the social identity-class ‘student/teacher’. The analyses which follow examine some of the applications and violations of these rules found in audio and video recordings of naturally occurring classroom talk (and transcripts thereof) for their orderliness as orientations to these rules. It is argued that the rules provide a systematic basis for the ‘feelings’ of ‘formality’ that researchers and participants have of such situations and that a decision as to the ‘formality’ or otherwise of a social situation can be predicated on the degree of pre-allocation involved in the organization of turns at talk in the situation. (Configuration and distance in interaction, conversational analysis, turn-taking systems, classroom language, sociology of education; British and Australian English).