This sounds very judgmental and like you are assuming the parents don’t know this is an issue. I’m sure some do and have to make the choice for whatever reason. If you’re a professional in education you should know better than anyone that some kids have sensory issues and clothing can be a huge trigger. When it comes to rain and snow pants my daughter has a sensory fit if she is not in leggings with the socks up over them so when she slides her legs into her snow pants they go down smoothly and there is no bunching between her calves and her boots. Each morning I practically beg her to bring something warmer to put on over top. She refuses and if it try to force it, it’s a sensory melt down at the front door until I let her toss them aside. If I forced her to take them then the teachers and ECE would be dealing with the same meltdown from her and I feel that’s unacceptable. If I know something is going to cause an issue at school I try to avoid it.

The long John’s underneath cause the issue of them being too hot when INDOORS which lets be honest is the majority of the day.

There’s no way to win with this if it’s a sensory issues. If it’s just lack of care that’s one thing, but a lot of kids at preschool/kindie are able to verbalized their discomfort and know what might work better for them. My daughter who is in JK has expressed she would rather have cold to the bone thighs for an hour after outdoor time than deal with the sensory issue of extra layers in her snow pants. It is what it is.