(notare l'orario leggermente piu' tardo) Using VLT spectroscopy and HST/VLT imaging of a sample of 18 early-type galaxies with 0.88<z<1.3 from the K20 survey, we study the evolution of the Fundamental Plane (FP), the Faber--Jackson and the Kormendy relation up to z=1.22. We find that the FP at z~1 stays flat, keeps a remarkably small scatter, and shows both an offset and a rotation. We interpret this in terms of evolution in the mass--to--light ratio and in the morphology (effective radius and S\'ersic index). We show evidence that the evolution rate depends on the galaxy mass, being faster for lower mass galaxies. We compare these results with the predictions of the hierachical models of galaxy evolution and discuss the possible factors driving the evolution of spheroidals.