"They get so frustrated"

They do. Ava cries at the strap. Leo throws the bag. Maya says "I can't" and pushes the form away. The frustration is real and it's loud and the takeover makes it stop, and if the point of parenting were to keep the volume down, the takeover would be right.

I'd put it differently. Frustration is what learning feels like from the inside, at the point where the wanting has arrived and the ability hasn't. Nobody is frustrated by a thing they can't do and don't care about. They're frustrated by a thing they can nearly do, and "nearly" is where all the learning is. If you take the job away at the first sign of it, you've taught something, and what you've taught is that the feeling means stop.

There's an old, small study that speaks to this. Audrey Hokoda and Frank Fincham observed twenty-one third-grade children with their mothers doing puzzles, some of which were solvable and some of which, unknown to them, were not. The children had already been sorted by whether they tended to give up or keep going when things got hard, which the researchers called helpless and mastery patterns. The mothers of the children who kept going behaved differently during the impossible puzzles. They stayed focused on the task and kept their mood up, they were responsive to the child's requests for help and to how able the child felt, and when the child said "I'm no good at this", they answered it. It's twenty-one children and the authors say to treat it with caution, and I do. But the picture it draws is of a parent who stays in the room, stays cheerful, and doesn't take the puzzle.

That's a different thing from doing nothing. It's not folding your arms while your child sobs at a shoe. It's staying near, saying "that's the hard bit", and not moving the strap. The frustration passes faster than you'd think when nobody makes it into an event, and it passes into something, which is the strap going through the right loop, and a face you'll want to remember.

One more thing. If the frustration is yours as well, if the third failed attempt at the zip is producing a voice you don't like, that's a different problem and there's an earlier book in this series about it, Not in front of the children. The takeover is sometimes a way of not shouting, and I'd rather you took over than shouted. But there's a third option, which is the margin, so that the zip isn't happening at the moment you've got least in you.