The over all website, physicsclassroom.com has a lot of links and categories to click through so you can refresh yourself with concepts you may have forgotten. Also in the categories on the side is a link to the NGSS so the website is geared for teachers as much as it is for students.
The webpage on conductors and insulators is full of examples, definitions, and explanations. It was diagrams and visuals of the electrons moving through certain objects so you can get a better understanding of what is really happening. It is a bit wordy and some of the material is a little dense, so if you are going to have your students read through it on their own, make sure you go through it and get ready for questions. It does have a lot of content, so it would be a good resource for you as a teacher to prep for a science class but if you’re teaching the lower grades, I wouldn’t have them navigating the site without you.