I think you have to speak to your director.
Leaving a kid "attached" to their socks is so sad, could she maybe see a way to get some extra clothing. (I WILL MAIL SOME SOCKS

Or springing for some vaseline. Maybe she could have a meeting or speak to the grandmother to get some permission....
Maybe the director doesn't really see it every day.
The director should have called CPS, you need to ask why she isn't doing that. A kid with sores so bad they are part of their own socks...crap give us your CPS office and we will all start writing letters (kidding of course).
Maybe even call 911.
I mean how are you or the director to know if she hasn't reached the septic point? Infection can get in any way.
And so quickly
I remember once playing with my friend at the park and her kids and my son was in shorts - legs fine. She is a GP so I am sure we'd have both noticed if there was something odd. Got home changed out of play clothes nothing. After dinner I got ready to give him a bath - took off his pants and I started to cry. He was a big oozing, pus filled mess on his legs about 4 inches by six inches. I took him straight to emerg got him oral antibiotics and the wound assessed and addressed. It was less than 4 hours from fine to disaster.
Or maybe look beyond CPS, maybe public health can help you out.
The parents seem so who cares maybe getting the director to draw up a letter to treat with over the counter stuff, vaseline, polysporin, etc. Someone might sign it on their way out the door. Does your director have a director?
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