I will come back and read the actual article later but from a purely practical, applicable view point, it really does save you the hassle of having to keep buying a shit load of clothes and keep constantly replacing them/buying new ones; that might be fine in the richer schools but in some of the less well off areas that might be a bit harder.
As for discipline i dont know about that...
I went to a catholic school who put on a really try-hard act to present themselves as looking as a private school. We had the whole blazers and tie thing (i hear public schools are doing that too now so i guess its less special...) but people would always find a way to screw with it. The chicks would roll up their skirt to make it shorter or the guys would tie their tie low (they even brought in those pre-tied ties for that reason). So, i don't really know about the discipline aspect, the people who would wear it properly would do so either way and the people who don't will probably keep doing that. Granted i didn't go to some elite school and like any regular school we had our share of idiots.
Our school had the fancy uniform, the government poured quiet a few several million into building one of those "Trade Training Centres" they promised at some election or another and they try to keep the place looking decent but to be honest its just a thin coat of varnish over the truth, our school did maybe slightly better than the public school around the corner and a couple teachers still couldn't put up with all the shit that went on and just bailed.
So, i guess the whole uniform thing does make the school look better but its just a mask really...