Griffen attended Agua Fria High School in Avondale, Arizona, the same high school as Vikings Hall of Famer Randall McDaniel. At Agua Fria, Griffen played as a defensive lineman and running back for the Owls high school football team. As a junior, he rushed for 794 yards on 142 carries for eight touchdowns, and had 12 receptions for 168 yards and one 71-yard reception where he outraced everybody for a score. On defense, he was double and triple-teamed but still managed 47 tackles, five sacks and three fumble recoveries. In his senior year, Griffen recorded 77 tackles, 16 sacks and a fumble recovery as a defensive end and ran for 1,251 yards on 159 carries (7. 9 avg. ) with 20 touchdowns and had 6 receptions with 2 touchdowns as a running back. His 2006 senior season honors included Super Prep Player of the Year, Scout. com Player of the Year, Parade All-American, EA Sports All-American first team, Super Prep All-American, Prep Star All-American, Scout. com All-American, Lemming All-American, Super Prep Elite 50, Prep Star 100, Rivals. com 100, Super Prep All-Farwest, Prep Star All-West, Scout. com All-West, Long Beach Press-Telegram Best in the West first team, Orange County Register Fab 15 first team, Arizona Republic All Arizona, West Valley View First Team, Tacoma News-Tribune Western 100 and Gatorade Arizona Player of the Year.