Every second, your kid’s brain takes in sound, light, touch, smell and movement, then decides what matters and what to ignore. That sorting job is what people mean by sensory processing. When the volume is turned up too high, ordinary input arrives like an alarm: the tag, the hand dryer, the crowded gym at pickup. When it is turned down too low, the signal barely registers, so your kid goes looking for more of it, crashing, jumping, squeezing and chewing, just to feel where their body is in space.
That is why nothing that looks like discipline ever moves it. You cannot consequence a nervous system into calibrating itself. It has to get the right input, at the right intensity, in an order that builds, and it has to practice. A comprehensive initial evaluation sorts out which channels are running too hot, which are running too quiet, and what your kid has already invented to cope. Find that, and the plan writes itself.