How to judge the quality of education of an art school? I know that most question in this community refer to (natural or engineering) sciences. This question is concerned with the quality of higher education in the field of arts though, I hope it is on topic here.  

My question goes along the lines of "What is the proper way to judge the quality of education of a university?". It is different from the question linked in that art schools have to be judged by looking at different metrics.
In user6726's answer to the question linked above, they state:


  [...] If students from institute X stumble more over questions at
  conferences compared to those from institute Y, or if they publish in
  lesser venues, or produce less-solid papers (more errors, more
  failures to think a problem through), then you can conclude either
  that Y attracts better students or that Y does a better job of
  training students than X [...].


Former students of an university of arts will not attend conferences as often as graduates from other fields, and rarely publish papers at all. While it is true that a university of art's value for a student's career is heavily dependent on the reputation of that university, this is not limited to the field of arts. Additionally, the reputation of an educational institution can be difficult to assess, if one is not in the same place and get hands-on experience there.

What should be considered when judging a university of arts, if one considers to study there?
This should be applicable to both undergrad and postgrad programmes.
Graduation rate, and time to graduation. A school with a graduation rate of 50% is not a good thing. Nor is a school with average time to bachelors degree of 6 years. Historically, the 'rejection rate' of students applying has also been a sign of school quality, although many schools (Harvard, etc) now game this by providing free or reduced priced applications so as to raise this rate. They also market like mad, so they can pocket your admission fee...