I Tweeted earlier today, Google has introduced some new options for filtering YouTube in schools. If your school uses Google Apps for Education you can now whitelist (approve for viewing) an entire YouTube channel instead of just individual videos. This means that if I want all of my history students to be able to access Tom Richey's and Keith Hughes' videos, I can approve the whole channel which includes current videos and any future videos that are added to it. That should be a lot less time-consuming than whitelisting each video as it becomes available.
Another new option is to give logged-in users access to YouTube on a strict, moderate, or unrestricted level. Google Apps administrators can change those settings for user groups or individuals.
You can learn how to enable any of these new settings in the YouTube settings support documentation offered by Google.