Thompson played on Bishop Montgomery's varsity team for all 4 years during his high school career. As a senior at Bishop Montgomery he averaged 22.8 points, 7.7 rebounds, and 5.4 assists while also leading his team to the CIF Open Division State Championship.[2] Bishop Montgomery beat Chino Hills, who were led by LaMelo Ball and his brother LiAngelo, in the regional semi-finals, and beat Mater Dei in the regional final before beating Woodcreek to win the state title.[3] Thompson participated in the Ballislife All-American Game on May 6, 2017. He led the game in scoring with 32 points on 14-of-18 shooting.[4]
Recruiting
On November 9, 2016, Thompson signed his National Letter of Intent to play for Oregon State, as he quoted, "I chose to attend OSU because I was impressed with the basketball facility, the coaching staff and the character of my future teammates. The opportunity to contribute as a freshman was appealing to me."
In his college debut against Southern Utah, Thompson scored 20 points, had 5 assists and grabbed 8 rebounds.[5] On March 3, 2018, he scored a season-high 23 points in a 92–67 win over Washington State.[6]
After his sophomore season, Thompson declared for the 2019 NBA draft. However, he withdrew from the draft on May 29, 2019, and returned to Oregon State for his junior season.[7][8]
As a junior, Thompson started 31 games and finished second on the Beavers in scoring at 14.8 points a game, while leading the team in assists at 4.5 per game. Following the season, he declared for the 2020 NBA draft but did not hire an agent.[9]