Writing the Script
The planning in the previous chapter leads to an actual script. What had been outlines and descriptions starts to take on details and images as the writer develops the actual words students will read and hear. A well-written script brings the content alive so that it can be recorded and created in tangible form as spoken language and visuals. It's the script that guides the rest of content development.
I recommend scripting the whole project including, obviously, the video, but also any accompanying web pages, animation, or other content. For the content reviewers, seeing it all in one document helps them understand the flow and logic and make sure nothing is missing or unnecessarily duplicated or explained in a sequence ...