I, personally, don't understand uniforms and strict rules at school. We don't have uniforms where I come from and were generally allowed to express ourselves however we wanted too (in terms of clothing). And I do think clothing is a way of expressing yourself.....Somethings weren't really allowed - like extremely revealing clothing, but all in all you wore what you wanted to.
There are standards at work but we don't have issued shoes to wear and if I wore trainers to work one day, someone *might* say something but I certainly wouldn't be sent home from work.
I don't agree with kids being sent home from school for something like shoes - they should be AT school, not sent home. A 'caution' or somethign similar or a discussion with the student's parents would be far more advantagous in my eyes. I think the school are being a little 'over the top', IMHO.