If you use a Google Site with your class (or as an eportfolio option), you can choose to have an announcements-style page, which functions similarly to a blog and has a built-in RSS Subscribe to posts link.
But never fear; there are other ways to incorporate subscription options to allow access to more visitors! note: if you are creating a site through a Google Apps for Education or Business domain, your domain must have Feedburner enabled in order for this to work.
For more, visit this Google Sites How To on RSS feed subscription.
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