I attended private school and I recall the talk of going to uniforms. They were talking about us having to wear navy blazers and white button downs. We really disliked that. However, looking back, I think we students would have accepted kahki pants and a standard white or blue collered golf shirt.
I think parents will spend much more money on trendy school clothing if students are not required to have uniforms. Give the parents a guideline, and let them choose where they want to purchase their clothes. I also think one of the biggest distractions in school is trends set by kids fashions. Not only is it a distraction, but it is also a stressful event as a kid, trying to fit in by purchasing the "right" styles and brands. Not every kid's parents are able to afford the trendy stuff as the seasons change. You don't see the football players getting to choose their own styles, nor do you see that with any of the high school team sports. Keep it simple.
In summary, I am 100 % for school uniforms and I do not see how it costs more money. I think it will actually cost less. The one downside which I see from making the kids were uniforms is that it teaches them to follow the orders from the higher ups, walk the straight and narrow (discipline), and that can stifle free thinking, and be rather dangerous depending on who their leaders are in life.