I had done this lesson last year as part of a Coding Club using Course 2 with 4th grade girls. I was not prepared to do it with 3rd graders. It was an eye-opener! I had the class with the most Learning Support kiddos in it do this first - and I really felt like I was talking a different language! The highest class got it with no problem, but the average ability groups were lost also. So I decided to cut up the grid paper and really focus on just doing a tiny piece of code each time I see them. I am having to debug what they don’t understand. Some want to write the arrows on the grid and some scribble in the NEXT square instead of the square that they stop in. This is going to be an ongoing process of following directions and taking it slow with all of my 3rd grade classes. I think it will be the first thing we do EVERY time they come to one of my class.
I posted a topic about this also. I believe the problem is not the difficulty of the assignment, but with the layout. Because the steps are listed in a grid box, they students had a very hard time truly understanding that it was NOT a grid to draw on.
When written on a long strip of paper or in two long rows like on the assessment, the students has WAY less problems.
Try the assignment with your groups and simply change the steps recording section to be something completely different looking than a grid box and see if that alleviates the problems in most of your students.