If this person is living in Arizona, then that state's law will control whether the children need to attend school. I'm not licensed to practice in Arizona, only in Oregon, so I can't comment on Arizona law; you might try re-posting in that state's forum. In Oregon, children between ages 7 and 18 are required to attend school up through the 12th grade (see ORS 339.010).
I do have to wonder, though, how you know whether this person will be enrolling their children in school, and why you care. If you're a parent to these children, then you have a right to seek custody and to try to influence their upbringing. If not, then your standing to compel any legal action involving them is likely quite limited.
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Oregon permits home-schooling under certain conditions. However, if these folks moved to AZ, Oregon likely will have very little interest in dealing with them, and it is now AZ's problem, if there is a problem. It seems unusual for an acquaintance (perhaps you have a closer relationship than you have mentioned) to be concerned about the enforcement of school attendance requirements in Arizona.
This comment is general in nature and is not intended as legal advice. It does not create an attorney client relationship and obviously is not confidential. You should contact an attorney in your area who can review with you all of the relevant facts and give you specific legal advice.