An unlikely friendship between a trash-talking guard and a quiet foreign forward was forged at Montverde Academy, a private college preparatory school in Florida.



D’Angelo Russell, who transferred in as a sophomore from Central High School in Louisville, Ky., and Ben Simmons, who had moved from Australia, won back-to-back national championships at Montverde in 2013 and 2014.



After competing against each other as teenagers in practice and leading Montverde to a 45-2 record, the two All-Stars are competing against each other on the NBA’s biggest stage, the playoffs. Russell leads the Nets, and Simmons is making his presence felt for the 76ers. The jerseys are different these days, but back at Montverde, there were glimpses of the players the two would become.



“D’Angelo, what stood out to me was his confidence,” Montverde coach Kevin Boyle said by phone. “He had just swag and confidence, a healthy cockiness about...