I was just going to post this. This is the answer to most people's parental problems with YouTube. I use this with my 7 year old. There is no way to do this easily and never for an average parent. Common Sense Media is my friend as a parent, but I have to lock down YouTube just to keep him from seeing something that no kid should see.

I use OpenDNS and I have a few custom scripts so I can learn how often certain sites are being used. "Too much of a good thing is still too much."

I use history on my daughters YT account with a quick script that compares her computer's history on her computer. I don't run it all the time but I tell her trust but verify a lot. She is doing her school online and our biggest issue is she will watch videos and not do here work for a few hours.