Discovery Education Free
Discovery Education (among many others) are offering this services and resources for free during the closing of schools. This includes an entire suite of videos, texts, lessons, primary documents, strategies, virtual field trips and more. I do not believe that this include the Discovery Techbook, but nonetheless a great learning resource for teachers to be able to share with students. As a Discovery Education Network Ambassador y personal favorites are their Spotlight on Strategies and Studio (used to be board builder).
A district representative must request access for the entire district at this time: