[1] He averaged 20.8 points and 8.2 rebounds as a senior and led the team to the Missouri Class 5 state title.

In Nike EYBL circuit, he played under coach Corey Tate with the St. Louis Eagles.

Barnett scored 43 points and collected 20 rebounds in an 86–77 overtime win against Columbia-Hickman in the championship game.

[4] As a senior, Barnett averaged 13.7 points and 5.7 rebounds per game and was one of the top 3-point shooters in the SEC at 41.4 percent.

He was arrested for a DWI on March 13, and missed the Tigers' loss to Florida State in the Round of 64 of the NCAA Tournament.

[8] On January 22, 2019, the Fort Wayne Mad Ants announced that they had acquired Barnett and Ike Nwamu from the Wisconsin Herd for Elijah Stewart and the returning player rights to Alex Hamilton.