Scat by Carl Hiassen

Bunny Starch, the most feared biology teacher ever, is missing. She disappeared after a school field trip to Black Vine Swamp. And, to be honest, the kids in her class are relieved.
 
But when the principal tries to tell the students that Mrs. Starch has been called away on a "family emergency," Nick and Marta just don't buy it. No, they figure the class delinquent, Smoke, has something to do with her disappearance.
 
And he does! But not in the way they think. There's a lot more going on in Black Vine Swamp than any one player in this twisted tale can see. And Nick and Marta will have to reckon with an eccentric eco-avenger, a stuffed rat named Chelsea, a wannabe Texas oilman, a singing substitute teacher, and a ticked-off Florida panther before they really begin to see the big picture.
 
That's life in the swamp, kids.