I think 3 of the dozen or so public schools around where I grew up had uniforms (lucky me, I went to one of them, ugh), while every private school (90% of which were some flavor of christian) had them. Most were more along the lines of 'dress code' than uniform though. I'm remembering khaki pants and bland colored polos more so than the blazer/tie/coat thing. It's probably because it's hot as balls on leather in the sun around here, so anything more than that would be killing kids or the AC budget.