Monk first attended East Poinsett County High School in Lepanto, Arkansas during his Freshman year. As a freshman, he averaged 22. 8 points, 4. 6 rebounds, and 2. 7 assist per game while leading them to a (25-8) overall record and an appearance in the Class 2A state championship game. After his freshman season, Monk transferred to Bentonville High School in Bentonville, Arkansas. In his junior year, he averaged 26. 6 points per game. In the spring and summer of 2015, Monk competed for the Amateur Athletic Union (AAU) team, Arkansas Wings Elite, on the Nike Elite Youth Basketball Circuit (EYBL) where he averaged 19. 7 points per game. He then competed on the 2015 Nike Global Challenge for the East team, where he averaged 22 points, 12 rebounds, and four assist in addition to earning Tournament MVP honors. On November 18, 2015 Monk committed to Kentucky, choosing UK over Arkansas. As a senior, he averaged 28. 6 points per game, 4. 4 assist per game and 7. 6 rebounds per game. In 2016, Monk played in the 2016 McDonald's All-American Game and Jordan Brand Classic where he earned Co-MVP honors alongside Kentucky teammate De'Aaron Fox.