[2] Plummer was named an honorable mention All-USA Arizona High School Team in the 2017 season.

[3] Plummer committed to play college football at Purdue University over other schools such as Arizona, South Carolina and Oregon State.

[4][5] Plummer made his first collegiate start at quarterback on September 14, 2019, against TCU, completing 13 of 19 passes for 181 yards, a touchdown and two interceptions in a loss.

[8][9] Plummer opened the 2021 season as Purdue's starting quarterback in a week one matchup against Oregon State.

[13] He was named the starter ahead of their season opener against UC Davis,[14] completing 23 of 35 passes for 268 yards and three touchdowns in a 34–13 win.