You laugh, but we complain about this a lot.
Up through middle school we would get project assignments from non-art teachers that involved what amounted to an arts and crafts project (eg, a history assignment that was a diorama about Lincoln or something).
My son always got bad grades on those projects despite having a B+ or an A in the class generally because art wasn't his thing, and the grading on the project was biased towards its artistic content. I would inevitably go in to gripe about the grade he got and I would see the high-scoring projects were nearly all by girls, many of whom seem to be into "coloring".
And nearly all these projects were assigned by female teachers. Their responses were really frustrating, a lot of bullshit about the importance of presentation quality of submitted work, etc. "What about their actual knowledge of the subject?" and the teachers would kind of blanch and not want to say anymore.
My take is there is some kind of low-level bias going on here, the teachers see the girls being less interested in the subject matter and toss them an easy one to boost their grades. Last year we only had two, and my *wife* actually did the artistic part of the work herself on one of them -- still only a C+!! My wife was super pissed and thought that it was a definite sign that the grade was being issued based on gender, not on content, because from a production value perspective it was like business-meeting quality.
This year during the fall "curriculum night" I actually asked all the teachers how many "coloring assignments" there would be. Most didn't understand and I explained, "You know, those assignments where we do something artistic that has nothing to do with the content of the curriculum and is judged on artistic merit". To a person, all the female teachers looked pissed that I asked that. Totally busted.