One useful but of course not absolute generalization is that grade school teachers "want to teach kids something" and high school teachers "want to teach something to kids." Which is to say that high school teachers are more likely to be motivated by subject first and grade school teachers are more likely to be motivated by kids first.

For something like computer science, It's going to be a rare person with a passion for computer science who jumps on the grade school track in a college of education. A grade school just isn't a place conducive to expressing that passion.