McLemore was born Feb. 11, 1993 in St. Louis, Missouri. He attended Wellston High School there for three seasons and was named to the St. Louis Post-Dispatch's all-metro team his junior year. He averaged 28.3 points, 12.7 rebounds and 6.2 assists that season. The school then shut down and McLemore was forced to transfer. He initially went to Oak Hill Academy in Virginia for his senior season, but transferred to Christian Life Center in Texas and appeared in six games. McLemore received interest from schools such as Ohio State and Tennessee before ultimately committing to Kansas.