When you called them lazy again
It'll happen. A bad morning, a third reminder, the kit on the bed, and the word will be out before the question has arrived. You'll see his face, and then you'll remember the columns.
One word isn't the childhood. The list will show a month with more Thursdays that went right than any month before, and one morning is one morning. What happened is that the standard is old and the question is new, and the old thing is faster for a while.
Put it right the same day. An earlier book in this series calls this the repair and gives it a chapter, and the short version is three sentences, said to the child, that day, without a "but". "I called you lazy this morning. That wasn't fair, you're nine and I should have had the list by the door. I'm sorry." A child who hears that learns something more useful than the word taught, which is that the adult can be wrong about him and say so, and that the label wasn't the truth.
Work out which standard got through. Was it a task that's moved to alone too early? Put the cue back. Was it a time of day when the child had nothing left? Ask less then. Was it a task you've never sorted into a column, so the adult-height standard was still on it by default? Sort it tonight.
No streaks. Don't count mornings without the word. Count Thursdays with the kit, and let one bad morning be one line in a list that's mostly ticked.
There's a slip that's quieter than the word, and it's the sigh. You didn't say lazy. You breathed out through your nose and looked at the ceiling, and he saw it, and it did the word's work. The repair is the same. "I did a big sigh at you this morning, that wasn't fair." Children read the face as well as the word, and a repair for a face is a thing they'll remember longer than the face.
And notice the child's face when you say sorry. In my observation it's surprise the first time, and then something like relief, and then, over months, a child who's less braced at twenty to nine, because the worst that happens now is a word that gets taken back.