I've run into the same problem over the years for my daughters (they're turning 11 and 7). During the school year it's not as much an issue because they wear uniforms to school but during the summer it becomes a nightmare to find them clothes that don't cry 'Skank in training'. I've resorted to second hand stores many, many times.
We've gotten a lot of her clothing at Salvation Army, consignment shops, etc. It's really the only safest way to go.
Every time I go to a department store, I continue to be amazed at how far these clothing manufacturers seem to be going in making children look like whores.
the sad part is the number of paretns who don't seem to care, and let their kids dress like that.