If they haven’t had any coding experience you might want to start the 3rd and 4th graders in course D - targeted to 3rd grade. There are some ramp up lessons at the beginning to make it easier for students who have never done coding.
But, honestly, my favorite course is course C. It’s targeted for 2nd grade but I think grades 2-4 would do well with it. This would make things easier for you since grades 2-4 would do the same online puzzles and you could teach the same “unplugged” lessons to each of these grades too. That way you will teach the same lesson many times - less prep - and each time you teach it the lesson gets better. The 4th graders will move through the lessons more quickly and maybe they will get to start course D at some point during the year.
Your idea of having the 5 graders do the express course is good! And, as you said, K should do course A and grade 1 should do course B.
You won’t go wrong whichever way you decide to do it. The kids are going to love it!
Let me know how else I can help. And please let me know what you decide and how it goes! What school are you at by the way?
Ps. There have been some updates to the courses and lessons. These updates were just put into effect on August 1st I believe. So I haven’t taught the courses with the updates yet. It’s possible that, with the changes, I may love courses D and E as much as course C!
You can also do the prescribed course allocation as follows:
K - A
1 - B
2 - C
3 - D
4 - E
5 - F
Some more ramp up lessons have been added to the front of courses E & F so theoretically 4th and 5th graders with no experience could start at these levels. But if you want to take it easier you can lump 2-4 and do course C first!