Apostrophe s

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A question from Kath and Tracy - parents who don't want to make any mistakes when helping out with homework! They ask:
What is the correct way to put an 's' on the end of a name that ends in 's' - e.g. James, this is James's homework? Or Ross: "Where is Rosses homework?" Which one is correct or is it by putting an apostrophe in?

Thanks you for your time