"They don't listen until I shout"
This is the same fact from the other side, and it's worth a chapter because it's said as a complaint about the child when it's a description of the ladder.
They don't listen until you shout. True. Why would they? Consider what the first ask has going for it. It's delivered from another room, to a child absorbed in something, in a normal voice, with no consequence attached and a track record of being repeated. There's no reason for a child to act on it, and children are economical. They act on what has to be acted on.
Think about who in your child's life gets listened to the first time. The teacher, usually. The swimming coach. Perhaps a grandparent. It's not because those people shout more. It's usually because they shout less, and because with them the first ask is the only ask. The teacher says "pencils down" once, and pencils go down, because in that room "pencils down" has always meant pencils down, and nothing has ever come after it except a consequence. Your child can do the thing. They do it every day at school. What they've learned at home is that the rules are different.
That's the awkward and hopeful part. The not listening isn't a fixed trait of the child. It's a fact about the ladder, and the ladder is yours. If you take out the rungs, so that there's one ask and then a consequence, the child will learn the new arrangement in the same way they learned the old one, which is by finding out what happens. It'll take a few weeks. It won't take years.
I'd add something about what the ladder does to your own voice. By the third ask, you're already annoyed, and the annoyance is in the ask, and the child hears it. So the third ask isn't a request. It's a warning of the shout, and it's heard as one, and some children, at that point, dig in, because being warned makes people stubborn. The sigh on Tuesday was your eight-year-old digging in. You then confirmed that the warning was real by shouting. Everyone did what they'd learned to do.
The quiet ask in chapter 17 removes all of this at once. There's one ask, so there's no warning stage. It's delivered close, so it can't be ignored the way a voice from the kitchen can. And it's followed by something, so it's real. Your child will listen the first time, because the first time will have become the only time.