An extra four fire engines were called in at around 6pm to help tackle the blaze at John Ray Infant School in Braintree.
More top news
It will be a largely cloudy but humid day with the risk of hit-and-miss heavy showers and thunderstorms.
It will turn dull and misty again overnight but it will stay mild. Tomorrow will be mostly cloudy with a risk of localised heavy showers.
Group Lotus has announced plans to shed over 300 jobs in a restructuring and cost-cutting move.