In foreign language, a semester long college course is often seen as equivalent to a year long high school course (or even more), so 6th semester college Chinese may approximate 6th year high school Chinese, although the exact correspondence may vary depending on the high school and college.
For comparison to AP level, you can look at sample AP Chinese questions at https://apcentral.collegeboard.org/courses/ap-chinese-language-and-culture/exam . Commonly, colleges consider AP score of 5 equivalent to 4th semester and AP score of 3 equivalent to 2nd semester, but colleges do vary (you can check the AP credit listing of the college you are taking the courses at).