[2] Braun played basketball for Blue Valley Northwest High School in Overland Park, Kansas.

As a senior, he averaged 27.8 points, 9.3 rebounds and 3.8 assists per game, leading his team to a third straight Class 6A state title.

[7] As a freshman at Kansas, Braun averaged 5.3 points and 2.9 rebounds per game, earning Big 12 All-Freshman Team honors.

In the championship game against the North Carolina Tar Heels, he had 12 points and 12 rebounds for his fifth double-double of the season, which helped Kansas rally from a 40–25 halftime deficit.

In the final possession of that game, he defended Caleb Love's three-point attempt, sealing the win and giving him his first NCAA title.