I-140 does not guarantee you to get GC(Green Card), even your kid has GC, after move to other state, he/she has to wait for sometime to be qualified as a local resident, then he/she can start to enjoy the local residents benefits. However, even you are H1, the kid is h4, after he/she moved to other state, after wait 6-12 months, he /she still can be considered as a local resident. The situation can be vary from state to state, you have to check the school where your kid is going to register for more details.