When you are using YouTube in class or for presentations, no one needs to know that you watch cat videos in your free time. You can purify your YouTube clips with ViewPure. Another great strategy for using clips with your students is to chop them and only show what you want. Use TubeChop for this.
The standards we currently use for art at AAS-Sofia are the Washington State Art Standards.
There are numerous excellent resources for art available on the web, including the Google Cultural Institute. There are several clips about it on their YouTube Channel here, including a clip below which will walk you through how to best use the site.