When I circumnavigated in the '70s, my then wife and I raised our daughter as we sailed. At that time one could buy a complete semester of learning, right down to the pencils, paper and erasers, never mind books and tests, from Calvert School. They were geared for American children being raised outside the country by diplomatic and military personnel.
They were excellent, well put together and geared for a student returning to just slip into the current curriculum of most schools stateside.
However, this sort of thing may no longer be available because of the internet, but perhaps you could find the equivalent online for today's education. Good luck.
