To get back on topic:
I think another mark of a good Dojang is one that makes its students feel part of something bigger within the Tae Kwon Do community.
I don't mean taking Tae Kwon Do students to Hapkido seminars or bring in Kuk Sool Won guest Instructors. I mean the Instructor is a valued and active member of the TKD community and the students are allowed to benefit from that experience. There are some schools where the Instructor has broken off from his teacher or is not active within the larger TKD community for some reason. So they teach and judge alone, and possibly bring in teachers from other styles because the Instructor does not have those TKD connections. The students learn in a vacuum.
Our organization has been fortunate to attend tournaments and seminars in various countries worldwide. Our Grandmaster is active with the world Tae Kwon Do community, and has allowed his students to compete against and train with other students and Tae Kwon Do Instructors around the world.
Additionally, at testings our students are fortunate to have judges from around the state and around the country, not just locally or just the Instructor.