Did you miss the quotes around "deadbeat"?
I'm sure that no one is actually calling parents deadbeats, I was merely using that word as tongue-in-cheek shorthand for "parent who does not take the school involvement expectation seriously enough." The more common word (that the kids will normally use) is "slacker." BTW, this is a private school.
The thing about using dress-down days this way is that the kids don't look at it as a privilege; they look at it as a given that on a dress-down day you dress down, and they consider it punishment to be required to wear their uniforms when everyone else is wearing jeans. In the higher grades the kids who are not in uniform tease the ones who are; there are lots of cracks about having "slackers" for parents.
The really offensive part AFAIAC is that the teachers are always given lists of which families had parents in attendance so that they can police the dress-down days, and the teachers invariably develop a subtle attitude about it. For instance, it will almost always be casually mentioned when you attend your parent-teacher conference. The kids whose names are always on the list are regarded as being from "fine families" while those whose
parents do not or cannot attend start to be treated as somehow pitiable.