I’ve come across a number of different bath products lately that are for kids - basically to make the chore of rinsing the shampoo out of their hair easier. There are a number of different “deflectors” they sell, but this one called Flo by Boon looks kind of interesting. It actually attaches directly to the bathtub spout, unlike some that I’ve seen that are handheld and looks sort of like a dustpan.

It functions just like a garden hose attachement, creating a flattened waterfall to make it easier to rinse. As a bonus it also has a bubble bath dispenser that can be activated by pressing a button.