Cool! I always liked messing around with stuff like this when I was younger. Even did something similar, but used a chemical reaction instead of the black light to get the required energy (basically a home made glowstick).
Did a quick web search to see if I could find the recipie and came up with this one that seems familiar:
Ethyl Acetate or Diethyl Phthalate (Solvents - unfortunately water won't work for this one - though it might be worth trying with the sharpie dye)
Rubrene (Dye)
Sodium Acetate (Base)
Bis(2,4,6-trichlorophenyl)Oxalate (TCPO)
Hydrogen Peroxide - 30% (Disolves the TCPO giving off energy which appears as visible light when mixed with the dye)
Again, same concept - takes non-visible energy (sorta with a a blacklight) and lets the florecent dye convent it to the visible spectrum.
I would think that the school's chem lab would have all of those ingredients (or substitutes, a little browsing on the web would help there), and he could probably talk a teacher into letting him try it. It's amazing what teachers will let you do if you write out your process and show that you'll learn something.
