The CFI attempted to demonstrate a short-field takeoff to his student, with a tailwind. He reported believing at the time that a light cross-wind/quartering tailwind was blowing. He elected to depart from RWY 27, because RWY 09 had utility wires at the departure end and a slight uphill gradient. During the takeoff roll, the airplane "lifted off slightly 1-2 times" and he held the airplane on the grass runway to increase acceleration. After rotation, the airplane climbed to about 15-20 ft AGL, and began to settle back to the ground. The nosewheel impacted a small ditch and the airplane nosed over. The airport manager reported that a 15 kt wind was blowing from the east when the accident occurred. A weather reporting station about 11 nm away reported winds from the east at 10 kts, shortly after the accident occurred. Based on performance data in the Cessna 152 information manual, the airplane was theoretically capable of a successful takeoff.