I agree with not making a huge deal about it, but your buddy should be ready with some facts in case the teacher states false facts.

This is some good info to bring in on death comparison with different drugs, alcohol, and pharmecueticals recorded by the US surgeon general:
Jack Herer - Comparison

And this is something he should also have with him:

"Drugs used in medicine are routinely given what is called an LD-50. The LD-50 rating indicates at what dosage fifty percent of test animals receiving a drug will die as a result of drug induced toxicity. A number of researchers have attempted to determine marijuana's LD-50 rating in test animals, without success. Simply stated, researchers have been unable to give animals enough marijuana to induce death.

8. At present it is estimated that marijuana's LD-50 is around 1:20,000 or 1:40,000. In layman terms this means that in order to induce death a marijuana smoker would have to consume 20,000 to 40,000 times as much marijuana as is contained in one marijuana cigarette. NIDA-supplied marijuana cigarettes weigh approximately .9 grams. A smoker would theoretically have to consume nearly 1,500 pounds of marijuana within about fifteen minutes to induce a lethal response. "

-JackHerer.com

That way he can respectfully counter any false claims his teacher may make, and prevent the brainwashing of other students.