Learn Zillion is a great site with high quality lessons built on Common Core Standards. LearnZillion is a learning platform that combines video lessons, assessments, and progress reporting. Each lesson highlights a Common Core standard, starting with math in grades 3-9.
The screencasts are exemplary – These could also be a model for students to create their own screencasts usingEDUCREATIONS app!
It is FREE for teachers and students. Worth checking out! http://learnzillion.com/