A 15-year-old boy is to appear in court charged with bringing a 15-inch knife into the school.
The teenager, who cannot be named due to his age, was arrested after a teacher confiscated a blade from a student on February 3.
Police were called and seized the knife.
The boy was bailed until Saturday, when officers charged him with possession of an offensive weapon.
He will appear at Croydon Youth Court on April 2.
A Metropolitan Police spokesman would not confirm which school the boy attended, but he was arrested and charged by officers from Fieldway.
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