We present the IniRobot pedagogical kit, conceived and deployed within French and Swiss primary schools for the initiation to robotics and computer science. It provides a microworld for learning, and takes an enquiry-based educational approach, where kids are led to construct their understanding through practicing an active investigation methodology within teams. It is based on the use of the Thymio II robotic platform. The paper presents the detailed pedagogical objectives and a first measure of results showing that children acquired several robotics-related concepts.