Needing prerequisites for projects doesn't usually mean more school.
Schools broadly fail to teach much. They don't work anyway. And they teach a lot of the wrong things.
Let's take an example. You want to write a novel. What are some of the prerequisites?
You'll need to be literate and able to type (already done, no worries). You should be better at grammar. You also need to know about plotting, character development, and what existing novels are like (what are some good things that your novel should have? what are some flaws in prior novels that you want to improve on?). You'll also need some project management skills. You're going to spend maybe a year writing the novel (or maybe five years while working a day job?). How do you schedule and budget your time? How do you organize your efforts over many different days and months, so it all comes together into a completed project? How do you finish the project instead of stopping in the middle? How can you know in advance what projects you'll still want to do six months from now? I suggest you start with smaller projects and shorter writing before a whole novel.
So anyway, do you need school to learn grammar? You already went to school and still get lots of commas wrong! Lots of schools don't even bother trying to teach grammar. When they do teach it, it's often a bunch of memorizing arbitrary-seeming rules and teaching to the test (just like how they screw up teaching math).
It is important for a novelist to know how commas work. But the default, standard approach to learning that should be using books and the internet. Look there first before looking for a course let alone going back to school. Try to educate yourself and consider getting education from others (which usually doesn't work well at all) as a second option if self-education isn't working. (BTW, if you can't educate yourself, I don't know why you think some teacher is going to fix your problem for you and somehow make your learning work well.)
Also, schools pretty much don't even teach novel writing skills or project management skills until college. 13 years of K-12 education isn't enough to fit it in, apparently. Novel writing isn't a skill everyone needs so it makes sense not to teach it to everyone, but do people really need to wait until age 18 to start learning it?
And with project management the assumption seems to be that you don't need to know it because there will be a boss who knows it and you'll just follow orders. That's the life they are preparing you for by only even trying to teach project management at business school for people preparing to be bosses. And keep all your hobby projects small and short since you never learned how to manage a larger project! Project management is something pretty much everyone should know a bit about, but it's left out of general education at schools!