Writing is a big part of the academic experience, at every level, for almost every subject.
Starting in grade school…

Students learn the alphabet, write short words, and tell simple stories with invented spelling.
In middle and junior high school, students tackle personal narratives, book reports, social studies projects, and science exhibits.
By high school…

Students must write lab reports, English essays, and history papers. They take notes, email instructors, and write for exams.
Starting on day one in college, professors assume students are fully prepared, ready to fill an exam book with cogent essays, or crank out 10-page MLA-style academic papers on deadline.
No wonder students who struggle with writing, struggle with school.