My understanding is that it wasn't really documented and so alot is not known about the evolution of poi. You could touch on the fire meteors of the ancient oriental cultures in ritual use (the bowls of fuel lit on fire, centripital(sp??) force kept it from flying everywhere, which had deep spiritual meaning). These seem to parallel poi in many ways and is similar in concept.
Obviously you will want to credit the Maori Rhythm Poi, however who first thought to light them on fire, who learned and spread it globally is a mystery, which is interesting in and of itself for students. In the search I did though I have really found no evidence of fire poi back before the 1960's.
As for staff, it's basis is very engrained in the Polynesian cultures, having been used in worship dance (some even to the goddess Pele) and in ceremonies for hundreds of years. It was thought a way to appease gods, to coax the elements and to really bring about a spiritual awareness. When tourism to the Polynesian Islands became very prevelant in the mid-20th century, fire staves (in many Polynesian countries known as fire knives and have a boxed shaped wicked heads, one of which is larger than the other) became popularized as a form of entertainment, just as hula dancing was and such. Of course this is the *much* abbreviated version. Oh, and traditionally, it is the art of the men, symbolizing strength and power.
I hope this helps at least a small bit!
Good luck with your class!
_________________________
Pele
Higher, higher burning fire...making music like a choir
"Oooh look! A pub!" -exclaimed after recovering from a stupid fall
"And for the decadence of art, nothing beats a roaring fire." -TMK