I think in this case, "essay" means something other than what you're thinking. I remember my DD getting such assignments, as early as K. They just wanted a small paragraph at most, and encouraged "developmental spelling." It drove perfectionist DD insane, because she wanted to do it right but the skills weren't yet there for what she wanted to do, and I saw the exercise as, "Let's let the children build up bad habits now that will be hard to break later."