I decline to comment on the shark, there's some good ideas out there though, pretty funny too :icon_razz
In all seriousness, the bear... Grizzlies are badass. They can run up to 55kph (35mph), they can climb trees, and their skull is much akin to a plate of steel.
All vital organs are buried under layers upon layers of muscle and fat, and it's brain is heavily protected by it's thick skull. Vital points are the mouth (of course), nose, eyes, ect.
Humans are just not equipped to fight a grizzly bear; it's too strong, too fast, and possess claws and teeth. We of course, unarmed, have none of these things. Even if 150 kids could "dog pile" a bear, what are they going to do to it? tickle it to death? Humans, even adults, lack the strength and natural weapons to inflict any physical harm, and would likely be killed in one hit by a massive paw.
I suppose it's like trying to attack an armoured tank with a BB gun. Humans are on top of the food chain because of our ability to create technology by manipulating the environment around us to better suit our needs.
I think without the use of the environment, our 150 brave little warriors are going to end up smeared across the forest floor. Give the little guys something! THINK OF THE CHILDREN!