In the summer prior to his 2014–15 sophomore campaign for Chino Hills, Ball suffered a foot injury, keeping him out of a tournament at Fairfax High School in June 2014. On September 14, 2014, he scored 30 points to beat Cathedral High School, 104–96, at the Ron Massey Memorial Fall Hoops Classic. He helped his team win the event by scoring 35 points, with seven three-pointers, in a title game victory against Maranatha High School. He averaged almost 30 points per game at the tournament and shared most valuable player (MVP) accolades with Lonzo. Entering the season, Chino Hills was ranked the 22nd best high school team in the nation by MaxPreps, and Ball, who was considered one of its key returning players with Lonzo, was joined by cousin Andre Ball. In the quarterfinals of a tournament hosted by Maranatha High School in December 2014, Ball tallied 53 points in a 111–80 win over Dorsey High School. He concluded the event with 33 points versus Maranatha as his team finished in third place. On January 31, 2015, in another win over Maranatha at the Fairfax State Preview Classic, Ball scored a game-high 36 points. Towards the end of his sophomore season, a severe ankle sprain sidelined him for four games, but he managed to return for the playoffs. On March 28, Chino Hills reached the CIF State Division I championship game, where they lost in double overtime to San Ramon Valley High School, 79–71, despite 23 points and a game-tying three-pointer in overtime from Ball. Following the season, on April 21, he verbally committed to play college basketball for the UCLA Bruins, becoming the program's first verbal commit from the class of 2017. He was rated a three-star recruit by Rivals. com.