My ds and dd both have nice school shoes for school. They both also have trainers for home and other shoes.
Both ask regularly if they can wear trainers as their friends do.
I think it looks awful and also think it's kind of disrespectful of the parents to send the children in trainers if the school uniform is black shoes. Lets face it you can get a pair of black leather school shoes from Asda for a tenner so I don't think there's any excuse!