Same request as the friendly request above to which I responded: what resources would you suggest for examples of "actual math" appropriate for elementary-age students.

I use a great variety of problem sources, published in both English and Chinese, to teach various learners of elementary math supplementary lessons, which is my current occupation. But one can never have too many sources of problems, so what sources do you suggest? There's no "ceiling" of difficulty level, because I have early-elementary-age students who are already well along in secondary-level math, so I have to keep looking for more challenging material all the time for my most advanced students.