Greetings All!
I'm new here, been composing off and on (more off than on) and trying to get serious in the last few months. I fall into the "mature" category age-wise but still young in spirit.
In answer to your question I took composition at a local community college for two semesters and it worked out well for me. I was surprised to discover that it was a one-on-one meeting with the teacher once a week, which was great. I could take the discussions anywhere I wanted and didn't have to go over material I was already familiar with.
Once I described my background we were able to move directly into me bringing in a work in progress and he would offer advice and comments. To his credit he didn't try to "help" me compose but offered hints in various ways.
Once someone has enough knowlege and skills what we need is an objective knowlegable musician who can provide feedback, not necessarily a "teacher" who provides information we don't already know.
As an example, he said one time, "As a listener, I would like to hear your theme repeated before you move into the next section." This was a revelation. I had been working on the piece at that time for about two or three weeks and had heard it so many times that the thought of repeating a section never occurred to me. He was able to provide the viewpoint of an audience member who was hearing the piece for the first time.
Of course, a trained musician as teacher can set you on the right path by teaching harmony, counterpoint, etc. as well.
If you can find the right person and circumstances, I recommend it.
Good luck.
Earl