Just to add, here in Argentina they required letters from my childrens' school in London stating that they had successfully completed their last year and all their final marks in letter format. These letters had to be signed by the head of the school and then legalised and translated.

Argentina and many other countries including France, do not allow children to automatically pass to the next year unless they have successfully completed the year. If they fail, they have to retake the year. These letters then help to decide which year they should be in and it doesn't relate to age, like in the UK.