David Toma is the ex-Newark undercover narcotics cop whose exploits served as the basis for TV's Toma and Baretta series. But this is principally about what drugs--and in particular marijuana--are doing to youngsters even before they reach their teens. By Toma's estimate 85 percent of all children over the age of ten experiment with drugs. He establishes his credentials by showing he's been there: the choking death of his five-year-old, only an hour after he had saved a stranger's child from the same fate, led him to pill addiction before a relative helped him out by showing he cared. Toma claims to have lectured to hundreds of thousands of kids--in 16-hour-days that embrace both a group address and private counseling--and he says he knew 20 years ago what medical science is only beginning to confirm: that marijuana robs children of the ability to concentrate; that it impairs short-term memory; that in some cases its THC concentration can lead to madness and unspeakable acts of violence; that it can cause reproductive damage--among both boys and girls--and eventually result in birth deformities. Whereas the marijuana of the Sixties contained a relatively low THC concentration of .02 percent, he argues, today's Colombian strains average about 6 percent; so the permissive attitude of teachers who were raised in the Sixties (and in many cases, he maintains, smoke with the children) is part of the problem. Toma is not above posing as a social philosopher; parents have to rethink their values, he believes, and not send mom out to work--particularly when it's more for luxuries than for necessities--while children are left to their own devices. And he is not above preaching--with all the fervor of a faith healer--by means of horrific examples: padded cells, eyes clawed out while on a high, murders committed that would otherwise have dissipated in anger, car accidents that took his friends' lives and left their children orphaned, etc. This lacks the credibility of an established medical authority, but it does manage to convey what an established authority might not be able to--passionate conviction on the kids' own terms, commonsense backbone-stiffening for parents who mistakenly try to give the kids too much ""space,"" and all-round been-there caring.