The film centers on the rivalry between two faculty members at St. Charles, an exclusive Catholic boarding school for boys. Joe Dobbs is an easy-going, well-liked English teacher, while Latin and Greek instructor Jerome Malley is feared and hated by his students. Malley is caring for his dying mother, and his stress is exacerbated by a series of threatening phone calls and written notes he receives. He's certain Dobbs is the source, but his caustic personality prevents him from winning any sympathy or support. Into the fray comes Paul Reis, a former student who has been hired to teach physical education, and he soon finds his loyalty torn between Dobbs and Malley, as he becomes increasingly aware of the latter's personal torments. Compounding his situation is the realization that the unbridled violence practiced by the students may be the result of demonic possession.
Roger Ebert of the Chicago Sun-Times gave the film 2.5 stars out of 4 and wrote "'Child’s Play,' which is beautifully acted and very nicely directed, doesn't seem to know whether it’s really about the supernatural or not... the entire movie is set up to suggests supernatural overtones, so when we get a rather conventional, Freudian, ending, we’re disappointed. The original fault lies with Robert Marasco's Broadway play, I suppose. But it could have been fixed for the movie." Vincent Canby of The New York Times wrote "With the exception of the performance of Mr. Mason, who is fine as the mad, exhausted Latin teacher, everything in 'Child's Play' seems to be rather cheaply tricky — such as the low-range photography and floor lighting designed to throw faces into eerie relief. In a more thoughtful film, the screen play and the performances might have been expected to create the sense of true menace and mystery. Even more irritating is the soundtrack, full of ominous clicking noises that are so loud and so resonant that one can't believe that the characters inside the film can't hear them, too." Variety called the film "a taut and suspenseful drama," further stating that "Sidney Lumet's direction catches the mood and spirit of an unhealthy situation and he makes every move count," and Mason gives a "solid performance." Gene Siskel of the Chicago Tribune rated the film 2 stars out of 4 and wrote "Because the look of the film is so artificial, and because the guilty party can be only one person — the only one with a genuine motive — 'Child's Play' is a small disaster as both horror story and mystery." A positive review from Charles Champlin of the Los Angeles Times called the film "a superior psychological thriller" that "works a few mild deceptions on the audience to achieve its ends, but no one is likely to care very much. Getting there is all the scary pleasure." Champlin added that "Mason's performance, in its power and also in its subtle shifting, ranks with the best portrayals in his long, impressive career." Gary Arnold of The Washington Post wrote "In a better play or movie we might have learned what makes one man despise another so intensely that he thinks he's justified in destroying him. In 'Child's Play' we get a load of ominous, evil-minded humbug, a vicious dumb show with schoolboys acting like zombie killers, constantly lurking in the shadows and inflicting nasty accidents."
