A modular construction kit for erecting a building is provided. The kit comprises a plurality of base track sections, a plurality of roof receiving tracks, and a plurality of wall panels. The base track is a U-shaped channel that extends around the base of the building and maintains the lower edges of the wall panels in a linear alignment. Wall panels include male, female, and hybrid (male/female) varieties, each variety having a different tongue and groove configuration on laterally opposing ends of the panel. Each wall panel has an outer skin and an inner skin separated by two divider walls and a structural bridge, which provide structural support across two axes. The roof receiving track is affixed to the upper edges of the wall panels to provide a supporting shelf for a roof structure. Thus, the invention is an easy to assemble kit for rapidly erecting buildings.