Set in a British public school (a fee-paying boarding school) in the late 1960s, the film opens as the pupils return for a new term. Mick Travis (Malcolm McDowell), Wallace (Richard Warwick), and Johnny (David Wood) are three non-conformist boys in the lower sixth form (the penultimate year). They are watched and persecuted by the "Whips", upper sixth formers given authority as prefects over the other boys, while the younger boys, the juniors, (whom the prefects degradingly call "Scum") are made to "fag" (act as personal servants) for the Whips. The Whips also make the juniors the subject of homosexual flirtatiousness.
Early scenes show the school's customs and traditions. The headmaster (Peter Jeffrey) is somewhat remote from the boys and the housemasters. Mick's housemaster, Mr Kemp (Arthur Lowe), is easily manipulated by the Whips into giving them a free hand in enforcing discipline. Some members of the staff are shown behaving cruelly or bizarrely.
One day, Mick and Johnny sneak off campus and steal a motorbike from a showroom. They ride to a cafe staffed by The Girl, and Mick has a fantasy nude wrestling encounter with her. Meanwhile, Wallace flirts with a younger boy Bobby Philips.
The three boys drink vodka in their study and consider how "one man can change the world with a bullet in the right place." Their clashes with school authorities become increasingly contentious. Eventually, a brutal caning by the Whips spurs them to action.
In a surreal sequence, they discover a cache of automatic weapons while cleaning out a storeroom. The Girl appears and together they commit to revolt against the establishment. On Founders' Day, when parents are visiting the school, they start a fire under the hall, smoke everyone out of the building, and open fire on them from the rooftop. Led by the visiting General who was giving a speech, the staff, boys, and parents break open the Combined Cadet Force armoury and fire back.
The headmaster tries to stop the firefight and calls for peace. The Girl produces a gun from her belt and shoots the headmaster through the forehead. The battle continues, and the camera closes in on Mick's face as he keeps firing. The screen fades to black, gunfire is heard, and "if...." is seen in red letters.
Where does the girl shoot the headmaster?
forehead