Portfolios are commonplace elsewhere on campus
As an undergraduate I wanted to take an art class for fun. I wasn't an art major but I liked drawing. I thought it would be fun. However, I was not allowed to register.
Art classes were only for art majors, and to become an art major I needed to submit a portfolio. Most universities restrict art class enrollment this way. Creative writing should do the same.
Some CW students have never read a book
At the beginning of each semester I gave an assignment called Great Writers are Great Readers. I gave everyone a 10-page handout listing "the greatest novels ever," which I told them was a purposefully incomplete and arbitrarily organized list. Their assignment was to highlight every book they had read and write an essay reflecting on what the highlighting revealed about them as a reader.
The assignment showed that most students had only read YA novels and a handful of others assigned in school. This was a reality check for them and they realized they needed to mature as readers if they were ever going to write.
Every semester I had one student who had not read a single book on the list. Not one. This was, and still is, hard to fathom. These were courses for juniors — for creative writing majors. I had purposefully included all the public school standards like Slaughterhouse-Five, To Kill A Mockingbird, A Separate Peace, Catcher in the Rye, and so forth, as well as popular YA novels. Somehow, more than one college junior had avoided reading anything at all, even for school. Did they ever read?
After talking with them I found the answer was no, they did not read. Then why were they taking a creative writing class? I still don't know. I'm not sure they knew. All of them were men. Two were ex-military with a strong interest in religion. I sensed they were men whose lives were in transition, who were confused, and perhaps they thought writing would help them sort out their lives.
Their presence negatively affected the class as a whole
Without exception their writing was the worst I had ever seen, with respect to both content and style. Their work was intellectually immature and their prose on par with middle and high school students. It was obvious they had never read a novel and had no idea what prose fiction looked like. They also contributed nothing to class discussions and were a liability in workshop, likely to offend their classmates.
I hate to admit the next part, but it should be said: their writing never improved. They knew so little, they couldn't understand the lessons or assignments. They did not know basic terms like protagonist, antagonist, climax, and point-of-view. There was only so much I could do for them in sixteen weeks.
Back when I was twenty years old, had I been allowed to take a drawing class in college, I would have been like these guys: lacking basic reference points and a vocabulary with which to talk about art. I had no experience — I hadn't even taken a high school art class — and wasn't ready for college-level work. At twenty, ego and impatience prevented me from seeing that.
What to do
Undergraduate creative writing courses need a barrier to entry, just like every other studio art course. This respects students who are ready for college-level work and deserve to be with equally matched peers. This would also benefit those who are not ready for college-level work. Allowing them into the course is an invitation to failure, and it's not fair to them.
That is not to say unprepared students should have no options. I strongly support offering introductory classes for non-majors at the freshman and sophomore levels. But to enroll in third-year classes, students should submit a portfolio of their work. It will be frustrating for some. There will be anger at so-called "elitism" from others. Nevertheless, it is in the best interest of everyone.