Mastering has two faces as a job:

• The artistic peer review act, which is to assess client's mix moves and either correct on master or suggest mixing adjustments.

• The industrial production act, which is to prepare and adjust sound material for its diffusion on final media (platform, CD, Vinyl,…).

A mastering engineer is a sharply skilled and experienced pair of ears who's responsible for those final touches that make impact. Sitting in a treated control room which he perfectly knows the sound of, he might be using snake-oil level analog/niche processings for that little marketing edge we all love to brag about, but whatever the gear, his mission is to provide the best sound finishing craftmanship to a sound producer.

Unfortunately, 80% of the learning part is acquiring those perception skills to fill the job, and it takes a lot of practice. Which goes far beyond the extremely limited session time and music exposure happening during a school course.

The most valuable things you do get by going to a school are (1) building an interesting network of people in the field which is a strong asset in the long time, and (2) get yourself some diploma credit for your resume. (1) can be extremely valuable and depending on school, (2) might open doors too.