A certified flight instructor (CFI) was providing instruction to a private pilot in a tailwheel equipped airplane. During the CFI’s demonstration of a simulated emergency landing, the airplane's speed got slow and made a hard landing with the right main landing gear and right wing striking the runway surface. The airplane was then flown back to the private pilot’s home airfield without further incident. A postaccident examination of the damaged wing by the airplane’s manufacturer, revealed that the rear spar was substantially damaged during the hard landing.