Elementary Science

I think the content regarding science here in Khan Academy is the most lower level science you can have. The prerequisites are almost nule. For biology and associates, no prerequisites. For chemistry, basic algebra and if you want to understand some formulas, basic calculus. For physics, algebra and trigonometry. All in an elemental level, just understanding relations. Calculus (up to introductory differential equations, i.e. Calc I) for wanting some small demonstrations. 

The math is the lowest level possible. And there are some sections where they invite you to think. Is awesome. 

Have you ever taught pk-5th? 

No, I didn't had the pleasure. Maybe you can introduce some videos where there is no math involved. As I said before, there is a section which I love called (I don't remember, check the Physics library) where they show some phenomena in a 1 minute video and you have to answer what is happening. From magnetic field to moment arm, those type of videos truly show a mastery on the material. The only thing I can suggest for the moment is follow the textbook, usually textbooks are great.

You have to realize that science has to be taught in PreK and Kinder with very little math because at ages 3-5 they don't have many math concepts (basic counting/ lower level addition and subtraction). So in basic elementary science concepts just first introduce ideas. Example physical properties in kinder might be separating by colors or shapes with concepts such as separating by magnetism, solubility, density introduced in 3rd-5th. Knowing how to teach them is not generally the issue. Especially in the current environment with lots of scholars not attending live classes, it would be an excellent option to use to help reach those scholars, as well as to help homeschooling parents in need of assistance of some format of alignment. This format also allows teachers to get data based on progress. Math is certain very well developed for elementary through college. They should do that as well for science.