Pshaw.
Chinese chalk is invariably the cheapest variety conceivable and it breaks constantly; sentences written on a chalkboard in China tend to look like they were written by someone who suffers frequent periodic seizures.
And chalk is dusty; one tends to finish a day of classes looking like a baker's apprentice.
Marker pens just get tired after a few words; the trick is to carry a quiver full of them and rotate them as they begin to fade.
And: marker pens allow one to fill lulls in a class by grabbing one, taking the top off, inhaling the vapors deeply, and lapsing into 30 seconds of uncontrollable giggling.
Actually, of course, marker pen vapors (unfortunately) have no psychopharmaceutical effects whatsoever, but I figure: WHY should we tell THEM?
One good thing I can say about chalk: The nub ends make excellent shrapnel for lobbing at the heads of sleeping students.
Oh...I had great luck with Powerpoint in the classroom. Just gotta know how to make a good slide that will serve as a focal point for discussion.
But now, back to our topic: whiteboard marker toxicity.
Marker pen vapors (unfortunately) have no psychopharmaceutical effects whatsoever.