On February 12, 2004, about 1720 Pacific standard time, a Piper PA-34-200, N55073, veered off the runway during landing and collided with a runway sign at the Hollister Municipal Airport, Hollister, California. American School of Aviation, Inc., was operating the airplane under the provisions of 14 CFR Part 91. The certified flight instructor (CFI) and the student pilot were not injured; the airplane sustained substantial damage. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight departed from the Reid-Hillview Airport, San Jose, California, at 1700, for the local area training flight. A Federal Aviation Administration (FAA) inspector reported that the airplane veered off of the runway during landing. The airplane then collided with a runway sign and the right flap was torn from its attachments, resulting in damage to the wing spar and ribs. In a written statement, the operator reported that the CFI and student were practicing a simulated single-engine approach. The student pilot lost directional control of the airplane after touchdown. The CFI elected to do a go-around. During the go-around, the airplane veered off of the runway and the right flap assembly impacted a runway sign. No mechanical malfunctions or failures were reported.