In regards to your kids / grandkids, are you more likely to back up school rules or tell the kids they can just disrgard a rule because it's stupid or whatever?

Picked up my 9 year old grand daughter from school today. She came running up, “Hi Gramma! I need to take this shirt back to the office!” She indicated a T-shirt she had on.
I said, “Why do you have to take it back to the office?”
“Because it’s not mine.”
“Why are you wearing it? What happened to the shirt you wore to school?”
She said, “Um…spaghetti straps.”
I said “I see. Well, you can turn it in in the morning, because you’re going to wear it home.”
On the way home she was bugging me to let her take off the T-shirt. I said, “No.”
She got a little huffy and started walking behind me ‘ignoring’ me. I just ignored her.
We got home and a couple of minutes later I realized she’d taken off the shirt after we got home. I said, “Brande. You should have asked me. I was going to let you take it off as soon as your attitude disappeared.”
She looked abashed, and looked down at the ground. I didn’t say anything more.
Then her Other Mother came to pick her up, and I told her there was that T-shirt in her back pack that needed to be turned in.
Amanda said, “I told her this morning that she wasn’t supposed to wear that shirt, but she insisted. I gave her a jacket to wear over it and said, ‘Ok, but you better be prepared to wear this jacket all day,’ but…apparently she didn’t.”
So we were both looking at Brande like, “Hmmmm?”
Again, she was abashed.
It was all very low key, but everyone was backing everyone else up. I think that’s important.

Now, as a disclaimer, there have been a few times I went to bat for my kids, and went and talked to the teacher and the principal, but I didn’t say anything negative about them to my kids. If I didn’t agree with something, I’d just tell my kids, “I’ll look into it.” Then I’d quietly go have a conference. I never said, “Well, they’re just idiots!” even if that’s what I thought. The problem at school would get resolved and that’s how they knew I got involved.

Other than important things, I backed up the school, even if I thought they were being silly.