Fire and Rescue NSW (FRNSW) crews have stopped a major fire from destroying a public school overnight at Orange in the state's central west.The blaze took hold on the top floor of a two-story building in the Maxwell Avenue school around 10.30pm, causing the roof to collapse.Seven FRNSW trucks and four Rural Fire Service tankers rushed to the scene where a number of classrooms and the school's library were ablaze.Support from NSW Police, NSW AmbulanceNSW Police, NSW Ambulance and energy company t