Because too many children experience the transition to school as a culture shock, during the past decade teachers have implemented so-called transition activities in order to bridge the gap between preschool and school. However, transition to school also calls for a development of higher mental functions, among others the development of children's learning motive. From the view of activity theory, transition to formal education entails crossing boundaries from the activity system of play to the activity system of school learning. The transition can be facilitated by developing a "transitory activity system", which mediates between the two systems, ensuring that the result of one system serves as a tool in the next. Advanced forms of play might make up a transitory activity system. The paper describes different forms of play crossing the boundaries of role-play (frame-play, aesthetic theme play and drama-play) which combine play, drama and philosophical dialogue to make up a transitory activity system.