The use of the "outdoors" in pre-school and school settings is becoming an increasingly important field of education and researchers have emphasised the positive influence of the "outdoors" on various social aspects. However, the facilitative conditions for such positive influences are not studied exhaustively. Therefore, we explored the conditions in "udeskole" influencing pupils' social relations based on an extreme case called the "Nature Class". In the "Nature Class" the pupils (third to fifth grades) were taught outside the classroom one day a week. Five pupils and two teachers were interviewed seven years after the period of "udeskole" to explore the conditions influencing social relations during the third to ninth grades. We applied a conventional qualitative content analysis and identified six conditions important for the improvement of the social relations. Four of them--"play", "interaction", "participation" and "pupil-centered tasks"--were important conditions for the positive social relations during the "Nature Class" project. Two conditions--"cooperation" and "engagement"--seem to be consequences of the improved social relations during the "Nature Class" project which positively influenced the pupils' abilities to cooperate and the pupils' strong engagement in the subsequent school years.