I work in an urban school system where there is a great deal of transience - it's not uncommon for kids to show up for a couple of months (having come to us from a different state), then abruptly taking off for another place. Even within our city, they often move. It's not unusual to see an elementary school-aged child with 10 different addresses written on their file.
That said, once a parent withdraws their child from the school district, we take it on faith that they will register in another district. But we have had more than one situation where there is a period of MONTHS before they do so. Usually it's a concerned relative or unusually observant neighbor calls social services, which is when we finally get a call requesting their records for the new school district. (Then the parent gets upset that their child has to repeat the school year, like...you kept him out from December through March! What did you think was going to happen??)
And homeschooling? Here in CT, all the parent has to do is sign one paper saying they are withdrawing their child in order to homeschool...and that's it. We do not follow up on the child in any way, not to ensure he or she is actually following some sort of curriculum, and most certainly not for physical well-being.
While no child ended up dying in these situations, I have long been extremely concerned about the potential for abuse and neglect. How many more children have to suffer before the states crack down on parental accountability??