The second generation, the inheritors, the trust-fund brats, so embarrassed by their parents who are so old-fashioned, so parochial, and all they care about is church and business, business and church.
So, if somebody is old school, he or she likes something that is a little bit old-fashioned, likes to do something a little bit old-fashioned, something that's probably outdated, not modern.
However conservative people very often dislike, and disapprove of, these new expressions which come into the language - and so I tend to be a little bit careful about who I'm talking to when I use expressions like this.
That language seems so old-fashioned if not exactly dated, to us now—the amount of detail, the sheer complexities of those stories and plots—but those were the novels I read that made me want to write novels.
For example, a friend of mine always does as she is told, never tries anything new or takes any risks. She has a bit of a stick-in-the-mud personality.