He was a starter during his senior season as his team achieved a 35–0 record and won the 1995 Class 5A boys basketball state championship.

[5] Mathis was selected to the All-Southland second team and was named by his coaches and teammates as the Bobcats' most valuable player.

[5] In his 1998–99 senior season, Mathis led his team in scoring for a second consecutive year with 17.6 points per game as the Bobcats finished with a 19–9 record.

[5] He was chosen as the Southland Conference Men's Basketball Player of the Year and named to the All-Southland first team.

[8] After his playing career ended in 2013, Mathis served as a clinician in partnership with Hakeem Olajuwon to develop basketball internationally, volunteered to provide outlets for student-athletes to earn collegiate scholarships and was a player development specialist for collegiate and professional athletes.

[3] Head coach Terrence Johnson stated that Mathis' connection to Texan basketball prospects would help with the team's recruiting efforts.