A combustion staging system has a splitting unit receiving and splitting metered fuel flow into out-going pilot and mains flows; pilot and mains fuel manifolds receiving the pilot and mains flows; and parallel mains flow scheduling valves distributing the mains flow. The mains flow scheduling valves pass the pilot fuel flow to injector pilot discharge orifices. Each mains flow scheduling valve has a chamber containing a piston, the chamber to a piston pilot side communicating with the pilot fuel manifold and the chamber to a mains side of the piston communicating with the mains fuel manifold. The piston is biased towards a closed pilot-only position preventing flow out of the chamber mains side to the injector mains discharge orifice. The piston is movable under increased pressure in the mains fuel manifold to an open pilot-and-mains position allowing flow out of the chamber mains side to the injector mains discharge orifice.