The flight instructor reported that, before the flight, he and his student inserted a calibrated wooden stick into the fuel tank to check the fuel quantity of the airplane and believed that it indicated just below ¾ tank, or about 16 gallons of fuel remaining. They completed the preflight inspection and proceeded with the flight to another airport for takeoff and landing practice. While at the other airport, they performed six circuits of the traffic pattern before proceeding back toward the departure airport. As they approached the airport, the flight instructor heard the engine speed decrease and initially thought his student had retarded the throttle, but she had not. The engine recovered briefly and then sputtered again. The flight instructor said he checked the mixture, master switch, ignition, and fuel pump settings, and the engine continued to have spurts of power. He surmised that they were experiencing a fuel issue and noted that the fuel gauge read empty. He notified air traffic control, and was cleared to land, but had insufficient altitude and executed a forced landing to a corn field. The airplane received substantial damage to the fuselage including separation of the empennage. Postaccident examination of the airplane revealed no usable fuel remained in the fuel tank. The flight instructor reported that he believed the time of day, weather conditions and lighting combined with an expectation bias, contributed to misreading of the fuel stick, which likely read below ½ tank before the flight. He also noted that he prepared a safety presentation about the event to present to flying club members and other aviation meetings. Based on the available information, the engine power loss was due to exhaustion of the airplane’s fuel supply.