While at Medina High School in Ohio, Allar passed for 4,444 yards and 48 touchdowns as a senior. He also rushed for 406 yards and nine touchdowns, and was named Ohio's Mr. Football. Over the course of his high school career he threw for 9,103 yards and 98 touchdowns.
Allar was a four-star recruit who committed to Penn State. After committing he was later give a five-star by 247Sports.com
In his freshman season at Penn State, Allar played in nine games, all coming off the bench, and completed 35 of 60 pass attempts for 344 yards and four touchdowns while also rushing for 52 yards and one touchdown.
In 2023, Allar started 13 games and threw for 2,631 yards and 25 touchdowns, while only throwing two interceptions.
The junior announced that he was coming back to Penn State for the 2025 season.