Two points from the Harvard Admission Officer:

They are well aware of the NCEA and Scholarship system, so you will not be at a disadvantage

The rigor of your courses matter more than your ranking (of course it would be great to have both). They understand that some people may have a higher ranking just because they took easier classes and so have a higher GPA.

If you have anymore Harvard specific questions you can also direct them to harvardconnection@g.harvard.edu where a group of trained Harvard students answer them promptly.

I cannot stress enough the importance of showing that you have challenged yourself. That you’ve taken that extra step people around you have not. If your school has limited resources or only offers x number of classes and scholarships, then try to look for online course, young scholar program, or enter more local competitions. There are many opportunities available to extend yourself and we’ll do our best to remind you of these opportunities on this page.