It depends on the state's definition of what it requires to be a "resident"...
Most states, I think, define a resident as having a permanent abode in the state with no preset intention or date of moving/leaving... Some, however, define it differently for students. So it is really dependent on the state that the school is in.
But on the other hand, I have seen schools give scholarships to out of state residents which equaled them being given in state tuition....