Although Letourneau was selected in the Ontario Hockey League draft, he elected instead to play at the prep school level.
[1] In the 2023–24 season, his second of two for St. Andrew's College, he scored 61 goals and a league-leading 127 points in 56 games at the U18 AAA level.
He also appeared in two games for the Sioux Falls Stampede of the United States Hockey League.
[3][4] In June 2024, Letourneau was selected 25th overall in the first round of the 2024 NHL entry draft by the Boston Bruins.
[5] In addition to hockey, Letourneau played basketball and varsity lacrosse in high school.