Philly SOR is great.  Super atmosphere that lets kids be kids, but also learn to be serious musicians.  My daughter has been at SOR for 3 years, and it was a great respite after her 2 years of classical lessons, which were great until she got totally bored with the music itself.  The model of performance rock is one that is perfect for kids who want to DO it.  Manager Craig Waxman and Music Director Noelle Hoover just make the place a wonderful environment for not only music learning and appreciation, but fun, craziness, and serious performance.