[1][2] He attended Christian Brothers Academy and played both quarterback and defensive back, leading the team to two Section III championships.

[4] However, as a senior he suffered a torn Achilles tendon and, as that put doubt on his college football career, Dennis decided to play a postgraduate year at the Peddie School.

[6] He saw more defensive action in 2020, appearing in 10 games, two as a starter, and posted a team-leading 14.5 tackles-for-loss, a total that placed top ten nationally, as well as 57 tackles and four sacks, on his way to being named third-team all-conference.

[4][9][10] In 2021, he started 13 games and led the team with 87 total tackles as well as 9.5 tackles-for-loss, four sacks, one blocked field goal, an interception and a fumble recovery, being named second-team All-Atlantic Coast Conference.

[14] After the regular season, Dennis declared for the NFL draft and skipped Pittsburgh's bowl game, finishing his college career with 233 tackles, 36.0 tackles-for-loss, 15.0 sacks, two forced fumbles and two interceptions.