St Albans Magistrates' Court heard how on September 2011 a 13-year-old pupil at the school was playing on a wooden swing in an adventure playground.
A Health and Safety Executive (HSE) investigation found the swing had collapsed because the supporting timbers had rotted. The heavy wooden cross beam of the swing fell onto the pupil's head and neck causing spinal injuries that resulted in permanent paralysis.
Queenswood School, of Shepherd's Way, Brookmans Park, Hatfield, was fined a total of £50,000, and ordered to pay £90,693 in costs after pleading guilty to an offence under Section 3(1) of the Health and Safety at Work etc. Act 1974.
Speaking after the hearing HSE Inspector Alison Ashworth said: "This case shows how important it is that schools and other providers of play equipment maintain them in a safe condition. This tragic accident could have been avoided had the school implemented the findings of its own risk assessment."