What do you do when…

When i say hello/good morning/good afternoon/goodbye to my kids, a good portion of them just stare at me and ignore me. Does this happen to anyone else?

I give my high schoolers a pass because I know what misery high school is (still think it’s weird and rude though). I have a couple elementary school kids who do it and for some reason it bugs me. Does anyone experience the same or find this to be rude? Do you just take it on the chin or make a quip? Genuinely curious. I obviously haven’t said anything to them when they do it but I’m just shocked at how many children just don’t have manners or common courtesy?