Surely not, if he spent all that time on his idea. Another two minutes with the spell check is nothing. On the other hand the teacher may be a good judge of character and can smell a rat. If the student blew off the assignment and tried to disguise his lack of effort in a bullshit essay wrapped in pseudo-profound thoughts and wordy sentences, he deserves a D for insulting his reader's intelligence. Regardless of the rare teacher who is the exception to the rule, most students can get away with spitting information back at a teacher in a introduction, three supporting paragraphs and a conclusion.
Form is what counts in most cases, forget all that crap about meaning and emotional content.
The content of writing for a teacher is rarely investigated, so students don't worry about it anymore. Anyhow, since we do most of our writing in our early years for teachers, this habit gets useful. Who doesn't want a good grade on an essay. I think about how many times a teacher comments on my good organization in a Theme paper. But this doesn't develop our writing as human beings rather than information spewers.