WordPress automatically archives everything by published date/time, so there's actually no need to do so manually.
What most sites do is simply post new content and stories to their categories. This will automatically refresh to your homepage and push the older content out of view. That way, you'll still have access to that older content when you, the author, or the reader needs it.
With WordPress, all archiving happens automatically as you add new content to your site. Only the newest content will be displayed on your homepage. Once content no longer appears on your homepage, it is considered archived. Archived material can still be accessed through search, category links, or staff profiles.
To control how many headlines show for each category on your homepage, you’ll need to edit the widget settings for each of your SNO Category Widgets.
The thing to remember about websites is that they handle continuous content -- the content isn't broken down by school year. That means that as you start publishing in the fall, there will still be a mix of last year's content with this year's content. After you publish enough stories, though, the homepage will show just this year's content.