From The Stargate Omnipedia
Instructor of Cameron Mitchell's graduating class from George Washington High School in 1987. He entered his class to find his automobile in the room, complete with a fresh coat of wax.
Mitchell, Darrell and possibly others had disassembled and reassembled his entire car to get it into the class, and later had to, again, disassemble and reassemble it to get it back out.
Bounty - Mitchell and Darrell tell Vala of one of their high school pranks involving Mr. Armstrong.