What is the protocol for learning baguazhang in our school?

Any student can learn baguazhang providing they have the aptitude.

Baguazhang is mandatory for dan-level students but optional for other students.
To qualify:

1. You need to have passed your yellow belt
2. You must know Yang Cheng Fu form (section 1) pattern to a reasonable standard

Ideally, a student should only learn baguazhang if their tai chi chuan is coming along well and they can demonstrate some aptitude at baguazhang.
It is important to see baguazhang as an extra, a bonus.
Baguazhang cannot be trained at the expense of your basic skills: qigong, Yang Cheng Fu form, partner work.