http://www.usatoday.com/story/life/...t-nbc-grace-vanderwaal-simon-cowell/90306694/ America's Got Talent will crown a Season 11 champion Wednesday night, but there's already a clear winner: the show itself. The NBC talent competition (tonight and Wednesday, 8 ET/PT) is again summer's top-rated program, enjoying its biggest audience in five seasons (an average of 13.7 million viewers, up 10% from last year) and its best performance with young adults since 2013. Besides naming a winner, Wednesday's finale will feature performances byStevie Nicks, Jersey Boys and Il Volo. Judge Howie Mandel attributes the increased popularity to a rising level of talent, especially among singers, that has accompanied the arrival of AGT executive producer and former American Idol arbiter Simon Cowell as a judge, replacing Howard Stern. (They join Mel B and Heidi Klum). "Simon created more of a gravitas to the judging panel; it's not just a talent contest, but stars can be made," Mandel says, referring to performers such as One Direction,Susan Boyle and Fifth Harmony who have competed on Cowell's X Factor. Contestants "come on with hopes of not just doing well in this contest but having a career beyond this, and singing in front of Simon Cowell means more than it ever meant before." Mandel marvels at the youngest competitors, including 14-year-old opera singer Laura Bretan and this season's breakout performer, singer-songwriter Grace VanderWaal, who's just 12. "All these really young people, younger than ever before, are showing up and doing things at a level far beyond anybody three times their age," he says. . She "is not only an adorable, little ukulele-playing singer, but an amazing, already accomplished songwriter who has caught the ear of everyone in the business."