The ordering of pages within a section is a convenience for the people updating the site. It is not relevant to people viewing the website, with an important caveat below. You can reorder the pages for your convenience.
The one place where the order of pages in a section matters is this: If someone types just the URL of the section, the default page is the first page in the section. So if you type …/undergraduate in the URL, you’ll get the first page in the "Undergraduate" section -- the page "For Undergraduates".
From the Dashboard:
Follow this same process to move pages in and out of sections and to reorder sections.