A receptacle assembly for a midplane connector system has a receptacle housing having openings receiving signal contacts and ground shields of a header assembly. The receptacle assembly includes contact modules coupled to the receptacle housing that each have a leadframe, a dielectric frame and a ground shield. The leadframe has signal contacts arranged in pairs carrying differential signals that are generally arranged along a leadframe plane with mating portions at ends thereof that have at least two points of contact electrically connected to a corresponding signal contact of the header assembly. The dielectric frame holds the signal contacts. The ground shield is coupled to a side of the dielectric frame and has ground tabs extending into the dielectric frame to provide electrical shielding between the pairs of signal contacts and grounding beams electrically connected to ground shields of the header assembly.