"Good" Writers

Can any student free of learning disabilities become a "good" writer?

When I think of writing, I think of an art form that can be taught to any and every student. However, I made it a point to call it an art form because it is these types of skills that can be mastered, which might not be attainable for every person. Take myself for example, I enjoy writing and conveying the thoughts I have; however I do not believe I am an excellent writer, but do consider myself to be a "good" writer. This leads me to assume the answer to this question is in the mind of the beholder and their own individual opinion on the definition of "good."

Does good mean you are the best writer in the world and have a million best-selling books?
In my mind this question does not have anything to do with being a good writer. Yes I believe that any student free of learning disabilities can become a good writer in a sense that they will have the skills and tools necessary to complete an assignment or task if asked to do so.