 Johnson attended Highland High School in Gilbert, Arizona from 2007 to 2009, before transferring to Findlay Prep in Henderson, Nevada for his junior year.As a junior in 2009–10, he averaged 14.1 points, 4.6 rebounds and 3.4 assists per game as he led Findlay to a 32-2 record.In November 2010, he signed a National Letter of Intent to play college basketball at the University of Arizona.