Anyone saying that school uniforms are a bad idea clearly never grew up with them, or was never bullied for being one of the poor kids. They're important.
But enforcing rules like these, where students are required to wear branded clothing, and the brand does not have options for Muslims, is clearly not okay.
Frankly, I don't like the idea of someone's religion making these demands of someone, but that's an entirely different problem. She's dressed just like any of the Muslim girls were at the schools I went to, and no-one had a problem with that.
The only time I can remember there ever being an "issue" was when one of my friends decided to start wearing a pinafore rather than a skirt, but it was permitted within the dress code - it's just that no-one chose to wear one. And that was the end of it.
The rules for uniforms should be that a skirt has to be black and no shorter than a certain length; e.g. must be worn to reach the knees, but anything longer is permitted.
Requiring branded clothing, beyond a specific tie or patch/trim to be sewn onto a blazer, is completely unacceptable for public schooling.
At best, these rules are extremely short-sighted and based on trying to make a profit off the uniforms - which should not be permitted. At worst, it comes off as Islamophobic. Neither is a good look.
But it also doesn't surprise me at all that this would happen, after my encounters with head teachers/school management. You have to wonder how some of them ever managed to end up in the position, and they certainly let that 'power' get to their heads.