I think the blame rests entirely on the parents' shoulders, pun intended.

1. For giving their daughter a garmet that they had to know violated dress code.

2. For permitting - even encouraging - her to wear it to school

3. For making such a big stink about it - that makes it more traumatic for their daughter

4. For giving her an "out" of switching to a private school - which teaches her that responsibility can be avoided by running away.

Beyond the parents, blame can be equally distributed, but they literally "started it" and are "prolonging it."