Phrasing for "Attended to different levels, ending (...) Advanced Level."

Which one of the followings sounds better.

• One year English course. Attended to different levels, ending at Advanced Level.
• One year English course. Attended to different levels, ending at the Advanced Level.
• One year English course. Attended to different levels, ending at an Advanced Level.

If none of them is correct. What would be a better way to phrase this? I’m trying to add this to my LinkedIn page. I personally would go for the second one, but I’m not completely sure.