Window seat, hood up, earbuds in. Sometimes the bus is the only private room a kid has.

Privacy is not the same thing as space. When every room you have is shared and every hour is scheduled, a seat by the window with your hood up becomes the closest thing to a door you can shut. That is not withdrawal, it is a person taking the only quiet available to them.

If that is where your quiet comes from, stop apologising for it. Let a few of those rides stay useless, with no homework and nothing to answer. And if somebody else is curled into a window seat, let them have it, because everyone is carrying a day you cannot see.