A wall system employing channel-reinforced lightweight precast concrete wall panels. The precast wall panels include a concrete slab, a pair of spaced-apart elongated generally parallel metallic side channels, and a plurality of spaced-apart elongated generally parallel metallic attachment channels. The side channels and attachment channels are partially embedded in the slab and extend substantially perpendicular to one another. Each wall panel can be coupled to a support wall by extending self-tapping screws through metallic wall framing members and the attachment channels at locations where the framing members and attachment channels cross.