@ all the people going on about current, voltage etc.
Voltage and Current go *together*. They cannot exist independently. Two points might have a potential difference (voltage) with respect to each other, but without a connection they have no current.
That said, yes 70mA can kill you; primarily by means of ventricular fibrillation. At a point past 110mA, the heart simply stops and restarts. This is what defibrillator does. That piece of equipment usually runs at 3000+ volts. The high voltage is needed because the resistance of the human body, through the skin anyways, is very high. They also use a conductive gel.
The little device employed by the wayward (pfft!) student won't kill anyone. Period. Even *IF* you were to connect it directly across someone's chest (which seems doubtful seeing that anyone smart enough to build one of these for fun is probably not that stupid) it still won't conduct enough to do harm. Remember the high resistance of the body? Resistance causes the voltage to drop across a conductor. With less voltage you get less current.
The skin contact resistance of the human body is about 5k to 10k. At 300 volts (and let's assume a resistance of 10k right hand to left hand) according to Ohm's Law the current flow would be I = V/R or I = 300/10000 = 0.03A or 30 mA.
Speaking personally, I too built a little stunner out of a camera flash and brought it to school. After they got over the initial fear that all stupid people have when they see something they don't understand (is that magic!?!?) they had a great time playing with it. They even asked me to build them some of their own.
It's becoming a very sad world; a place where curiosity and wonder are cruelly stamped out and replaced with indoctrination. This reminds me of that piece entitled "Mentor's Last Words".
"My crime is that of outsmarting you, something you will never forgive me for."
We need to separate school and state. There is a great article about this actually by a fellow named Sheldon Richman. http://jim.com/schools.htm