Over the Edge by Hal Friedman

An eight-grade class trip from a supposedly perfect and affluent little town to a state forest ends in a horrifying moment when a revered teacher plunges to her death from a towering cliff. If the students present witnessed the events leading up to the accident, they're not telling.

No one in the elite and tight-knit suburb of Knollwood, New Jersey, seems to know what really happened to the teacher. Worse yet, no one seems to care. Except Meg Foley. A young, single woman used to instructing inner-city kids, Meg gladly accepts a replacement position in this cushioned community. But in the eyes of her new students she sees a chilling hint of past terrors, and Meg is determined to find out the cause.

In her search for the truth, Meg raises painful questions that the people in the town would rather not answer: Was the teacher not what she seemed, not even close? Did a rebellious clan of teenagers take their revenge on a tough, critical authority? Or was it some greater evil that no one dares to acknowledge?

The hornet's nest Meg stirs quickly results in antagonism from school and local officials, as her quest probes a lot more than just a tragic but isolated incident. When unseen forces in the community target her as their enemy, first with threats, then with violence, Meg can no longer handle the danger alone.

At her request, Meg is joined by maverick Los Angeles police detective Dan Jarrett, her father's partner before his death in the line of duty. Jarrett must protect Meg and discover the truth about a teacher who never expected the result of her last assignment and a town that fiercely protects its own.

Mrs. Wilkens prayed silently for someone to help her. She looked over her shoulder as she continued to flee. She couldn't see or hear them any longer but was certain they were still behind her, somewhere.