Because I have had a couple questions about my daughters step stool, I thought I'd take a moment to show and discuss it.
It may look very simple, and it is, but I actually put a little bit of thought into this bench before it was made. I knew it needed to last, it needed to work as a seat for her, but also it needed to be a step stool for working at my bench. All of that and not be so light that it would tip over.
The bench is made from 2 x 10 Douglas Fir from the home center. I hand planed everything to remove the cupping, but for the most part it is as thick as I could keep it. The thick stock gives it the weight it needs to not tip over so easily, that's why its so thick and blocky.
I do see the writing on the wall though. Eventually as she gets bigger and starts to use things like hand planes, I will need to build her a platform to stand on while working at my bench, but for now the little stool still works.