If I had a dollar for every time someone has asked this question (and $10 for every time there's been a newspaper or magazine/journal article about it) I could retire. Of course, as someone who teaches creative writing myself, in a Diploma level course, I'm going to say Yes, it can be taught. I wouldn't be doing this job if I didn't believe that. But there are always going to be arguments. I have a quote on my desk that says something like "A creative writing course can't teach someone how to write, but it can teach someone how not to write." To me, that's step 1.
We select students for our course. That means we read their folio of writing pieces, we make them sit a grammar and punctuation test (because we've discovered the hard way that someone who has no grasp of how to use the language will fail our course, and we do fail people, especially in the editing subjects, but it affects every subject they do), we make them do more writing after the test, and then we interview them. Does that make it sound hard to get in? It is. We have 25 full-time places, and we get about 120 applicants. So to be offered a full-time place, you have to show some kind of talent, a good grasp of the English language and a commitment to writing and reading.
I say "a good grasp of the English language" because far too many applicants coming out of Year 12 in high school have appalling grammar and punctuation skills. So we can't and don't expect applicants to be perfect in that area - that's why they have to do a whole year of grammar, punctuation and sentence construction, plus some editing. And why a commitment to writing and reading? Because if you want to be a writer and you aren't writing on a regular basis (even a journal) and you don't read, you're not on the right track. Maybe you should be something else.
So if step 1 is teaching people how not to write, what is the rest of it about? Teaching them to read like writers is step 2 for me. Asking 'what is this writer doing? how are they doing it? what can I learn from it?' is a huge, ongoing learning process. I'm still doing it myself after 20 years of writing and publishing, and I expect to be doing it forever. I want my students to do it too. We teachers aren't going to be at their shoulders after the course is finished.
Step 3 is writing. Lots. Not just the novel, or a short story or two, or a picture book or two. Writing every day. Writing many things. Writing in different styles. Writing background material and backstory in order to create a work that has depth and complexity. Writing poetry to increase language skills and appreciation. Writing scripts to improve dialogue (or if you want to write scripts, writing character backstory to improve how your characters speak). Writing to deadlines, because why shouldn't you learn to write under pressure? And editors expect you to meet deadlines in the real world. Creating your own deadlines and making writing contracts with yourself, so that you are writing thousands of words every month.
Step 4 is revision. Not just a little polishing and editing, but re-visioning the whole work, if it needs it. Learning how to 'see' your own work with a critical eye. In the course, we do a lot of workshopping and critiquing. In first year, everyone is more tentative, more fragile, and the teachers are firm but encouraging. In second year, I'm tough, and I expect everyone to toughen up. I'm not mean and nasty (and neither is anyone else allowed to be) but if something is not working, then the writer needs to address it fully and rethink what they're trying to achieve. Fiddling around the edges and changing half a dozen words very often is pointless. I try to teach students to be brave about their rewriting, and also to be tough on themselves. Many stories only truly find their full potential through the re-visioning process.
There are other things we teach - mostly to do with craft and how to write better, how to develop aspects you are weak in, how to outline and plot so your novel doesn't fall in a hole - but what we also teach is the industry. How publishing works, how books get accepted, what happens next, what marketing is all about, how to market yourself, how to be professional at all times. And how to stay motivated and set goals.
And after this long post, I still feel like there are a million more things I could say about what we teach in our course, but I'll stop here.