Gardner concluded his three-year varsity career at King's Fork High School in Suffolk, Va., with 1,431 points and 992 rebounds under head coach Josh Worrell. He became just the third player in school history to collect more than 1,000 points.
Gardner was an All-Eastern Region selection in 2009-10 after helping the Bulldogs to their second-straight district championship and third-straight district tournament title. He was also voted the city's player of the year and was tabbed to the all-city team. The squad, which has claimed 48-straight wins in district action, finished the year 24-3 overall and saw its season end with a triple-overtime setback in the regional quarterfinals.
Tabbed to the Virginia High School Coaches Association Group AAA All-State Team and all-district squad (second-straight year) as a senior, Gardner averaged 22.2 points, 12.2 rebounds and 2.1 blocks per game. He also collected 21 double-doubles in 27 outings.
As a junior in 2008-09, Gardner was a second team all-state honoree and helped King's Fork to the Group AAA state championship, claiming a 49-47 win over Williams Fleming HS in the title matchup. He averaged 15.6 points and 7.6 rebounds per contest that season for the Bulldogs, who finished the season 31-1 overall.
King's Fork claimed the district tourney title in 2007-08, Gardner's first campaign with the varsity squad.