The concrete blocks pictured on the floor of the engine room look like "beds" for diesel generators.
I would have thought the diesel engines would have been used to power the searchlights.
Second World War searchlights include models manufactured by General Electric and by the Sperry Company (of gyroscope fame). These were mostly of 60" (152.4 cm) diameter with rhodium plated parabolic mirror, reflecting a carbon arc discharge. Peak output was 800,000,000 candlepower. It was powered by a 15 kW generator and had an effective beam visibility of 28 to 35 miles (45 to 56 km) in clear low humidity.
Most of the school was probably hooked-up to the National Grid i.e. barracks etc, but you simply couldn't obtain 800,000,000 candlepower from household electricity.