The implementation of the new physics curriculm for Italian high school requires that, starting from 2014-15, modern Physics, and in particular Quantum Physics, be taught in the last year of the high school (students age 18-19 years). For that reason a considerable effort has been done this year inside the National Project Piano Lauree Scientifiche to respond to schools' requests of support both for helping teachers in deepening the content matter and for designing new approaches, adequate to students' age and preparation.
Moving from an established research line on the educational use of the sum over paths method, we worked with in-service and pre-service teachers with the aim of favouring a gradual and effective approach to quantum physics, starting from Feynman's picture of the photon. Classical experiments on the wave phenomenology of light, such as interference and diffraction, are reconsidered by using commonly available materials: measurements employ a video camera and the Tracker software; the sum over paths analysis of interference phenomena is introduced through GeoGebra simulations.
Then experimental evidence making both the purely wavelike and classical corpuscular interpretations of light untenable is discussed. Some of the experiments we consider are: ``granular'' interaction of light with matter (photoelectric and Compton effects); indivisibility of the photon; single photon interference. Stressing in particular the importance of the last point, we introduce the Feynman conception of the photon and the probabilistic interpretation of the sum over paths method. Modern experiments such as the Zhou-Wang-Mandel experiment are discussed to better characterize the peculiarity of quantum object behaviour, in particular the measurement problem. Finally the sum over paths method for massive particles and quantization are introduced. The sequence has been tested both with pre-service and in-service teachers in the perspective of implementing it in schools.