The original building of this children’s school was located in the centre of the plot which had, at that time, a U- shaped layout; its concave side organizes the main entrance from the street, and between the convex side and the rest of the limits of the plot, it generates the playground for the students' breaks. Basically, that was a normal way to put together some classrooms around a court. The constructive conditions of this building were those of a traditional one. Thick structural walls made of stones that support a light wooden made roof structure nowadays replaced by a steel one; an insubstantial building.We had to incorporate a new program that consisted in a secretary’s office, a staff room, a lunch room and a kitchen, toilets and a heating installation room, and also a covered space for the breaks in rainy days.Given that the new program had to be developed on the ground floor and the only option to make it was using the court behind, that, due to its shape and dimensions, made it difficult to work. The goal was how to improve the condition of that back court. In the end, the program is was conceived as wrapped elements or volumes that generate a piece of larger magnitude with a clear continuity from the beginning to the end, trying not to exhaust the available space and giving enough architectural quality to be lived to all the programme.The new path is a kind of hybrid prosthesis-bypass that, starting in the main entrance, connects the entire new programme arriving to the second corridor. A new element that is connected to the main artery gets blood irrigation or circulation for this new area. For that we started doing some previous interventions that prepared the patient to receive the new organ: Locate the heating room in a central part of the building; organize the definitive entrance from the front schoolyard and make the path lead to the entrance again as a loop, using what we call 'the second corridor'. The main handicap was how this concept could be tangibly experienced by the people when the work had finished. That is why the constructive decisions became really important. The difficulty of working in that back yard made us plan the design as an assembly construction instead of a traditional brick one. It consists of a steel structure coated with enamelled metal plates for the exterior, and pre-made gypsum sheets for the interiors. These materials are easy to transport and place, they speed up the work at the same time as configuring the construction as a light element with an easy assembly appearance. Rather than built, assembled.The exterior is designed with a clear and probably hard definition; the interior strives to be a pleasant walk full of different experiences. Something occurs in every metre intentionally. How the floor and ceiling are manipulated, the layout of the lights and windows and the attractive green coloured walls, make this programmatic optional path a unique architectural experience.