Place one 26-inch by 18-inch section of plywood on a flat surface, laying horizontally. Select one 24-inch by 4-inch section of plywood and apply wood glue to the 4-inch edge. Press the 4-inch glued edge along the top of the 26-inch side. The 4-inch by 24-inch section of plywood will run 4-inches from the top corner of the 26-inch edge down toward the bottom corner. The 4-inch by 24-inch plywood will stand up in the air, requiring you to hold it in place for one minute while the wood glue sets.
Carefully turn over the 26-inch by 18-inch section of plywood and drive two screws through the back edge of the 4-inch by 17-inch plywood to secure the hold.
Repeat Steps 1 and 2 with the remaining 4-inch by 17-inch section of plywood. Attach the remaining section along the opposite 26-inch side, along the same 18-inch end. This will create a structure that looks like an L-shape when viewed from either side, or a U-shape when viewed from either 18-inch edge.
Place structure in standing position, resting on the 17-inch by 14-inch plywoods as well as the 18-inch edge. Line both exposed 4-inch edges with wood glue. Press the remaining 18-inch by 26-inch section of plywood onto the glued edges. Drive two 2-inch screws through each end of the 4-inch wood joined to the 18-inch by 26-inch plywood section. The structure should now appear as a U-shape when viewed from the side with the 4-inch by 17-inch plywood.
Line the top-exposed edges of the 4-inch by 17-inch plywood sections with wood glue. The structure should remain in a position where it appears to be a U-shaped structure when viewed from the side. Press the 17-inch by 23-inch section of plywood onto the glued edges. Drive one 2-inch screw every 4-inches along each of the 17-inch edges. This will create a base for the desk top.
Place a 24-inch by 18-inch section of plywood on a flat surface. Measure in 3 inches from each corner along one of the 24-inch edges. Attach one door hinge at each 3-inch location using 1/2-inch screws.
Flip the structure over. Place the 24-inch by 18-inch plywood section over the top of the desk structure. Place the 24-inch edge of the 24-inch by 18-inch plywood along the top 24-inch edge. Place door hinges along the inner edge, and attach the hinges to the interior of the desk using 1/2-inch screws. Flip the top down. Students can flip up the top for storage.