Watch great documentaries online for free
See the referenced article at: http://aceonlineschools.com/15-best-websites-for-free-documentaries/
Here’s a pretty comprehensive list of 15 sites hosting documentaries for free viewing.
The content spans award-winning documentaries to films more directly related to school curriculum. The sites have done the hard work of vetting the content for you, which makes them handier that YouTube is for parents and teachers who often have to scour the humongous YouTube database for hidden jewels. The comparable offering from YouTube would have to be the Documentary & Biography category in the YouTube Movies channel.
A couple of small caveats though. Sites such as Hulu (which is on the list) do not allow viewing in all geographies due to licensing restrictions, and some sites do have popular movies as well in their inventory in addition to documentaries. Definitely a link to bookmark and keep handy.