I suspect there is actually more to this story.
Consider: 1) This is not a public school, which means that the student is there by choice. 2) There are other private schools (I know of a few on the west coast) that could actually provide a wi-fi free environment with little trouble. 3) Moving is easier than a lawsuit.
From these datum I conclude that the lawsuit has a purpose quite apart from it's stated one. My conjecture is that the child has gotten into some form of trouble, and the school was on the verge of suspending or expelling the child. This lawsuit might well be a ploy to make it effectively impossible for the school to expel the child, since any such action now could easily be construed as discrimination.
When I assume that then this whole thing makes a lot more sense.