There's no clear cut answer to that, but my personal opinion is that 'Old School' is just as Russell describes.

I guess I see myself as 'Other' - ultimately I don't follow any teachings, but have learned dribs & drabs from others- one who could be described as an Old School submissive.

Mostly I do what I believe is right, preferring to fit the D/s to who I'm with, rather than following a set of rules. I agree with this line from Russell 100%:
A Dom treasures his sub and knows that he must be careful in all things because he is taking her on a journey of the mind that can hold some bad surprises for both of them.
You can also find a lot of info online, much of which is contradictory, but still interesting.