The purpose of this article is to study and analyse how two te achers implement an outdoor situation for children aged 4-5 in a Swedish preschool. The analysis and interpretation of the data in this paper has been influenced by situation theory and by the use of the didactic contract as a key concept. The term didactic contract is seen as a metaphor; consequently, I use a broader definition of the didactic contract to illustrate how the role of the teacher aff ects the communication of mathematics with children. Most of the text in this paper is adapted from my thesis (Delacour, 2013) and articles (Delacour, 2014a, b).