I think it's an innocent mistake. I have driven my son to school on a closed day by mistake. It was lame. I knew something weird was going on as I approached the trafficless street and turned into the nearly empty parking lot
I wasn't working at the time so it was just as much a pita to go through the 'hurry up, get dressed, eat your breakfast, get in the car, etc, etc," all for nothing haha.. Sucks that they had to inconvenience you (unnecessary early wake up booooo)with their mistake, but I wouldn't read too much into it. I mean I don't think it means they are thoughtless, selfish, ungrateful for your services etc... Just a mistake. And I have a school calendar, but I can't imagine double checking it daily in case the day is a holiday that I hadn't realized. Labor day isn't as apparent to many people as something like 4th of July. I'm home with my kids- if it wasn't for Facebook and another parent mentioning being off Monday, I probably wouldn't have noticed it was a holiday myself. Probably the fact that she doesn't work is what contributed to her not realizing.