Recommendation for a Copy Editing Course?

[Nicole]

I am an English teacher and have been in the classroom the past ten years. I have also indie published two of my own novels. I recently started Beta-Reading and intend to add proof-reading to my services. While I am well-versed in rules of grammar and sentence structure, I'd like to take a course specific to copy-editing to decide if it's something I'd like to offer to other writers. I've looked around online a bit (although not exhaustively), but I was wondering if anyone in here has taken a course or gone through a program that you recommend in the U.S. Thanks in advance!