It kind of depends. In my state, if a student is expelled from a public school, no other public school (district or charter) has to accept him for a year after the expulsion. If he was expelled and happened to have an IEP, then yes, the law still requires the school find another option. But that's generally going to be some kind of an alternative school, and at that point a lot of families try to figure out a private or homeschool situation on their own rather than face alternative school.