。
Police seized a large quantity of drugs at the school.
Literal
Police [topic-は] school [at-で] large-quantity [of-の] drugs [object-を] seized.
News-report register, typical of an 事件 (incident/crime report) summary. 薬物 is the legal/technical term for 'controlled substances, drugs' — more formal than the casual 麻薬 or the slang ドラッグ. 押収 is a legal/official word specifically for police or customs seizures. 大量の 'large quantity of' emphasizes scale. The spare, SOV-clean structure is characteristic of news writing.