CONCERTS The preteen guitar heroes in Seattle’s School of Rock are infinitely cooler than I was at their age. Not only do they look the part—with Mohawks, skinny jeans, and a power guitar stance worthy of Slash—but they also play some fine rock ‘n’ roll. And then there are the shy ones, the kids who prompt the stage mom in all of us to yell "Sing out, Louise!" But they’re there to learn, and we’...