A comprehensive radon survey of 2372 rooms in 348 Northamptonshire schools is reported, together with results of the successful mitigation of the raised radon levels found in 20 schools. From analysis of the occupancy of affected rooms and the costs of remediation a total cost of £19 400 per man-sievert saved annually was derived. This is around four times more cost-effective than the radon remediation in Health Service premises in Northamptonshire, and slightly more cost-effective than a domestic programme where all householders with radon levels above the Action Level carry out remediation. As only a small percentage of householders undertook remediation, a schools' remediation programme is the most cost-effective programme to reduce radon in an Affected Area.