While websites like YouTube are frequently looked at as entertainment portals, there are lots of great educational videos on all manner of topics including: math, language arts, science, social studies, technology, and more.
With that said, there are some guidelines that should be followed by parents or instructors when it comes to finding content for children on a topic.
Use consistent sources
Many of the videos are a part of channels that produce similar content on a regular basis, and use a familiar style from video to video. It can be useful for increasing comprehension, specially for complicated topics, to use videos who fit an established pattern of information.
Always review sources
Even the best channels sometimes have a video that may not be up to par compared to their usual offerings. Before showing a video to your children, or students, make sure it meets the standards for content that you have.
Be ready to answer questions
Even the most in depth of content is going to have gaps, or provide less than desired detail on a finer point or two, and it is important that the teacher or parent is prepared to speak intelligently about the subject beyond just the content of the video. It can be useful to have a few other videos or websites that cover specific portions ready for continued learning.