Kit of building blocks for constructing educational electronic circuits comprising a ferromagnetic base plate (10) with the diagram (21) of the circuit to construct. A transparent plastic sheet (30) covers the diagram. A group of magnets (40, 41) rest on the plastic sheet attracted by the plate (10). The surface of the magnets (40, 41) is electrically conducting. A plurality of building blocks can be detachably mounted on the magnets (40, 41), each magnet (41) connecting the steel sheets (702) of the building blocks that rest on it. The steel sheets of the blocks are designed so that the attraction forces that arise between the magnets and the sheets drive the modules exactly to a desired equilibrium position.