A teaching kit comprises a board (1) and a plurality of component tiles (5). Each component tile bearing an electrical or electronic component (4) and connector means (9) such that the component tiles (5) may be connected together to form a circuit. The board (1) and each of the component tiles (5) has cooperable magnetic means so that once a component tile has been positioned on the board it is held magnetically in position. Thus with the teaching kit, children using the kit can build their own circuits and learn electrical theory or electronics as they do so.