When somebody says (and not in the most modern parlance) that they are kicking it old school, they are generally referring to wearing clothing (and possibly hair styles) which are far beyond out of date. It is interesting how, after a certain amount of time, a particular type of ensemble can actually take on a whole new life of hipness as a retro piece. What follows is one probable theory as to why this happens, and why it is most likely never going to stop happening until such a point as there is no more new fashion.
When a particular bit of fashion has been worn for awhile, people begin to get tired of it. Soon enough, they move on to something entirely different, and people who are fashionable do the newest thing. It becomes easy enough to identify which people are not with the times, because their fashions are consistent with that preceding era. In most cases, looking more than a year or two out of date is a cause for ridicule, especially among the most fashion conscious circles of people. After all, people have to keep their groups (and their group consensus of how the world works) in tune, which involves having both an “us” and a “them” to consider.
However, as time goes on and the stigma about what just went out of style fades (usually after a few other fashions have joined it in the “donate” pile coming out of people’s closets), people began to remember the good times that they had while wearing (and being surrounded by) those fashions. This allows a person who spontaneously falls back into a past style to carry a positive association, which contributes to the notion of looking “Retro.” While nobody wants to be out of style, a lot of people who like to ride a countercultural wave (or make one) love to be retro.