Oh wait, I see where you're going. It actually has nothing to do with school at all, since they were under the age of 19 on Dec 31 of the tax year. (At least, I am assuming they were NOT 19 on or before Dec 31 of the tax year.)
Of the five requirements, the first two (relationship and age) are met. So nothing there.
For the 3rd requirement of the Residency test, "To meet this test, your child must have lived with you for more than half the year. There are exceptions for temporary absences, children who were born or died during the year, kidnapped children, and children of divorced or separated parents."
I am not aware of any publication that I can find that specifies or indicates that serving in the military is a temporary absence. So if they departed home for basic on or before Jun 31st of the tax year (taking into account it's a leap year) they don't meet the residency requirement.
