If you are applying at an Embassy for student entry clearance (sometimes called a "visa" in everyday speech, although it's not a visa), the onyl academic documents you need are those that demonstrate your intention and ability to follow the course. As a native English speaker with an unconditional offer, that should usually speak for itself, although an ECO might ask for evidence of your previous academic progress to double-check.
If you have been studying in the UK already, and you are extending your stay for further study, either by applying to the Home Office in the UK or via an Embassy overseas, you need to provide letters, transcripts, etc that show your attendance and progress on the course has been satisfactory so far.