On July 10, 2003, about 0800 mountain standard time, a Cessna 172S, N787WW, porpoised during landing at Deer Valley Airport (DVT), Phoenix, Arizona. As a result, the firewall and engine mounts were bent. Westwind Aviation was operating the airplane under the provisions of 14 CFR Part 91. The student was not injured; the airplane sustained substantial damage. Visual meteorological conditions prevailed during the local area instructional flight and no flight plan had been filed. The flight departed from Deer Valley at 0700. In a written statement, the student reported that he had been practicing maneuvers in the practice area and was returning to Deer Valley to land. He extended his downwind leg due to traffic in the pattern and entered final approach "a little high." He "flared too high, slowed, and landed flat." Then, he "porpoised [the] airplane and landed nose gear first on [the] second touchdown." He felt the damage occured on the second touchdown. He then performed a go-around, did a second go-around after being too high on final, and landed on the third approach without difficulty. The student did not report any mechanical difficulties with the airplane prior to the accident.