This is an interesting situation. The student has a green card, which means he does not have any limit to apply schools. If your future academic plan for your son is to send him to one of top universities, this is the right time to start preparation.
I think your son’s case is a little different from others, I need to have more information such as your son’s current school records, possible locations for school, parent’s stay with the student in USA (in this case, good public school or private day school would be the option), and others. I strongly recommend you to visit some of good professionals who might be able to consider all options and give you the best possible advice.