Google Sites allow users to create CMS websites as part of the Google suite of free tools for an organization. Google Sites are a great choice for education because many schools are going to Google Docs as their main system for student and teacher access and storage. However, just like any CMS, a learning curve exists, and teachers do not want another mandate thrown their way without proper training. Without a useful template, Google Sites are really quite plain and only somewhat user-friendly, which will result in haphazard, poorly-maintained teacher sites. Passive Ninja has developed several templates for one school district and can come into any district to create a professional style that allows updating without making the process too much to handle for educators already taxed for time.
Integration of Google Drive to Google Sites should be the #1 priority, as this allows certain individuals skilled in using a CMS to develop the site while everyone else just uses documents. However, those documents are not searchable as web content, so an administrator must understand the distinction.
Honestly, Google Sites can look almost as pretty as any free web tool out there, especially if those end up charging an arm and a leg to host. If you want your own domain name, then choose Joomla. If you want to be able to do it yourself, just make a Facebook page. However, if you have a lot of content that you want to display in a way that makes sense to viewers, Google Sites might be the right answer.