Lighting is a major part of energy consumption in buildings. Lighting systems will thus be one of the important component systems of a smart grid for dynamic load management services like demand response. We consider the problem of control of multiple lighting systems in a building for providing demand response service. In the scenario considered in this paper, under a demand response request, lighting systems in a building react by executing dimming control to reduce power consumption based on their load shedding flexibilities. Load shedding flexibility reflects the amount of power reduction that can be achieved by an individual controller without violating minimum illumination requirements of occupants in that area. We consider different methods for distributing load reduction across the multiple lighting system controllers employing their respective load shedding flexibilities. The performance of the methods is compared with a scheme where uniform dimming is applied across the lighting systems.