Well, those are terms which sort of defy definition. Some argue it's a riding style, others that it's an attitude, still others that it's nothing at all. Here are a couple of selected posts which express the opinions of their respective authors:

(The following from: Jason Chu, jchu@mail.trincoll.edu)

Guys from Old School probably started boarding around the mid to late 80's when the Burton Safari and the 1st generation Sims ATV came out. At this point in boarding, we were running our back foots kinda straight across with Sorels. The "trend" at this stage was to evolve boarding to a more ski/high tech thing. Stances were going tighter and more angled, hard boots were getting more consideration (I'm sure old Damian helped out here..), and asym's were starting to flood the market. This is not to say "freestyle" and pipe riding was declining. However, sometime later (92?), there was a backlash towards more trick oriented boarding with heavy emphasis on bilateral abilities. In order to be fully symmetrical with a lot of fakie oriented moves, the board really requires a rider to have his feet straight across, wide for stability, and the board to be fully symmetrical (did barf make the first real "twin-tip" board?) Thus boarding reverses its trend and this is where I believe "New School" arrived. I remember the days when guys would laugh at you if you rode a perpendicular stance. Anyway that's how I view it.

(The following from: Mark, mbock@cdinet.com)

I was always under the impression that the difference lies mainly in tricks and overall style. Old school tends to be big on huge air, grabs, a nice carvey riding style, bigger boards, freeriding, etc., while new school tends towards shorter twintip boards, flatland tricks, spins, a really wide stance, lots of time spent in the park as opposed to freeriding the slopes, etc. (A lot of this difference is reflected in skateboarding, I'm told by a friend who's been skating since the mid-80s.)

>...is it as trivial as the old bunch of stylin' snowboarders turning 20, and thus ceasing to be relevant? :-)

Well, yeah, that too, probably... :)

(The following from: Dave F., daveer@aol.com)

... When I started riding there were no freestyle bindings. I've stayed pretty up to date with the technology though, and ride a fully symmetrical Barfoot (a recent one, not the one from the 80's) with pretty much 0/0 stance angles. But I still consider myself "Old School" when I have to make the comparison (and I don't like to), because I consider the difference to be mostly an attitude thing. Perhaps this may be inaccurate, but I've always associated "New School" with the whole lame, commercial, gangster imitating, skier dissing, baggy pant wearing crowd of (worm)heads who have of late started giving the sport a bad name and sparked quite a few closures to snowboarders around the country.