Writing long texts for school is stupid and it is a skill that is in practice purely developed in order to do homework. I am not surprised it immediately declines as soon as the necessity is removed.
People write a lot of stuff that is not for homework. Maybe they should make a measurement of something else they write. I would even say that writing for homework is a special skill in bullshitting that does not (cannot) exist in other forms of writing.
> ...is a skill that is in practice purely developed in order to do homework.
I would argue that it helps kids learn how to organize and formulate coherent thoughts and communicate with others. I'm sure it helps them do homework, too.
"Writing is nature’s way of letting you know how sloppy your thinking is." -- Guindon