In high school, Bol was considered one of the best players in the class of 2018, having been rated a consensus five-star recruit and earning McDonald's All-American honors.

[3] In 2001, the family traveled to Cairo, Egypt, where they were stranded for many months due to visa problems, despite having acquired tickets to the United States from American friends.

[6] As a 6 ft 5 in (1.96 m) seventh grader, Bol featured in a highlight video[7] at an Indianapolis basketball camp that drew attention from CBS Sports[8] and The Washington Post.

[10] For the beginning of his freshman basketball season, Bol played for the junior varsity team of Blue Valley Northwest High School in Overland Park, Kansas.

[6][11] Bol made his debut for the Bishop Miege junior varsity team on December 11, 2014, displaying his shot blocking and shooting ability.

[14] In May, Bol played for his under-15 Amateur Athletic Union (AAU) team KC Run GMC at the Jayhawk Invitational in Kansas City, Missouri, scoring 15 points in one game.

[17] Bol contributed 14 points to help Bishop Miege win the Kansas Class 4A Division I state title game, 69–59, over McPherson High School in March.

[20] In November 2016, Bol announced that he was transferring from Bishop Miege to Mater Dei High School in Santa Ana, California for his junior year.

[22] Bol debuted for Mater Dei on January 24, 2017, recording 21 points, 10 rebounds, and 3 blocks to coast past Orange Lutheran High School.

[24] He scored 15 points in a March 4 loss to Bishop Montgomery High School at the CIF Southern Section Open Division title game.

[25] On March 14, at the Open Division semifinals, Bol led Mater Dei with 15 points and 6 rebounds as they defeated St. Augustine High School.

[26] He averaged 16.5 points, 8.6 rebounds, and 2.9 blocks per game as a junior, leading his team to a California Interscholastic Federation (CIF) runner-up finish.

[27] In May, at the Nike Elite Youth Basketball League (EYBL) with his team California Supreme, Bol averaged 25.4 points, 9.9 rebounds and 4.1 blocks per game.

[32] Bol scored 32 points in 21 minutes, shooting 14-of-17 from the field, in a January 14, 2018 rout of Immaculate Conception High School at the Spalding Hoophall Classic.

[35] Bol finished his senior season at Findlay Prep averaging 20.4 points, 8.2 rebounds, and 2.4 blocks per game, earning All-USA Boys Basketball Second-Team honors from USA Today High School Sports.

[40] After recording 20 points, 9 rebounds, and 4 blocks in a 66–54 win over San Diego on December 12, Bol injured his left foot and missed the rest of the season.

[65] In April 2018, Bol drew attention at the Nike Hoop Summit, playing for the United States junior national select team.

[2] He recorded 20 points, 9 rebounds, 6 assists, and 5 steals in an 89–76 loss to Team World, which was made up of international players playing high school basketball in the United States.