The use of virtual agents in social coaching has increased rapidly in the last decade. In social coaching, the virtual agent should be able to express different social attitudes to train the user in different situations than can occur in real life. In this paper, we propose a model of social attitudes that enables a virtual agent to reason on the appropriate social attitude to express during the interaction with a user given the course of the interaction, but also the emotions, mood and personality of the agent. Moreover, the model enables the virtual agent to display its social attitude through its non-verbal behaviour.