Perhaps we should adopt the international law of domicil, still used in some cases with an international element. That says that you have a 'domicil of origin' which is the domicil of whatever country your father was domiciled in. This can be changed to your 'domicil of choice', which is of the country of which you display a permanent and settled intention to live in and belong to , meaning, in effect, that you intended to die there. That is more than would be displayed by someone who decided to, and did, play football in a country for five years, whether they were educated there in that time or not.
Can't think that the education rule, if it exists, is of universal application. It would have no use for someone who was over the school leaving age when they started. Suppose they were 18? Or, recently, 16 ?