Keith Chandler, 63, was working as part of a team at Brentwood School Charitable Incorporated Organisation replacing part of a bay window at a residential flat in the school grounds.
Chandler was standing on the window's roof when he fell 2.6 m after his foot became caught. He was taken to hospital with chipped vertebrae and a broken collarbone.
The Health and Safety Executive found there was no guardrail on the top of the bay, or any other means of protection to prevent the workers from falling. There were also no supervisory arrangements.
Brentwood School Charitable Incorporated Organisation pleaded guilty to breaching Regulation 4(1) of the Work at Height Regulations, as it did not properly plan and supervise the replacement work for the window, and failed to ensure the task was carried out safely.
The school was fined £40,000 and must also pay costs of £1,477.
