His family then moved to Texas, where he attended Plano East Senior High School, which employed a spread offense.

Clayton led his team to the Illinois High School Association (IHSA) 6A state championship and a perfect 14–0 record.

[1] In 2008, Clayton completed 152 of 258 pass attempts for 1,894 yards, 18 touchdowns, and four interceptions,[3] before he suffered an injury that forced him to miss the final three games.

[1] Prior to the 2009 season, Clayton is ranked 13th in terms of passing yards for a UNLV quarterback after having played in just 16 games.

[4] The New York Times predicted UNLV to reach bowl eligibility in 2009 largely because of Clayton, who when healthy, "can score enough points to keep the team in most games".