In the movie, the students are kept in place through a very concrete system (they must 'check in' with bracelets that they wear, the implication being that if they fail to register they will be killed or punished in some way. This concrete, visible system of keeping the students from running away differs entirely from the novel, where the reader was left to assume that the only thing keeping the students at Hailsham, at the Cottages, and ultimately bound to their lives as carers/donors, were the messages they had internalized that this is the only life they could ever possibly live.
