[Activity for Schools] This activity demonstrates the generation of pairs of entangled photons through the process of Spontaneous Parametric Down-Conversion (SPDC) in nonlinear BBO (Beta-Barium Borate) crystals. Participants will perform a simplified Bell test, adjusting polarizers and recording measurements to directly observe the violation of the CHSH inequality —an experimental proof of quantum entanglement. Each session includes a short introduction, the execution of the experiment, and a final discussion of the results. The setup requires a dark room, standard electrical connections, and the support of trained staff to guide and supervise the activity. A unique opportunity to explore, interactively and accessibly, one of the most fundamental phenomena in quantum mechanics.