The cost-effectiveness and cost-consequences of a school-based social worker intervention: A within-trial economic evaluation

• The SWIS trial compared a social worker assigned to schools (intervention) versus usual practice. • The mean total cost of the SWIS intervention per school was £106,771.30. • Variations in staff recruitment to SWIS teams led to differences in costs for local authorities. • Costs were re-estimated to account for staff time and quality of implementation. • The probability of SWIS being cost-effective for averting a section 47 enquiry at cost-effectiveness thresholds was low. Schools are a significant source of referrals to Children’s Social Care (CSC) services. A within-trial economic evaluation estimated the cost-effectiveness of embedding social workers in schools (SWIS) in England compared to usual practice. Two hundred and sixty-eight schools comprising 277,888 students were randomised. The primary outcome of the trial was section 47 enquiries (i.e. child protection referrals to CSC services). The economic evaluation estimated the incremental cost-effectiveness of SWIS in reducing section 47 enquiries. Micro-costing approaches assessed the cost of the social worker intervention and addressed variability in key unit costs. Mean differences in costs and outcomes were estimated, with bootstrap 95% confidence intervals and scaling to incidence rate ratios per 1000 students per year. No statistically significant differences between trial arms were identified for any outcomes, costs or cost-effectiveness over a 23-month follow-up. The probability that SWIS is cost-effective was estimated for a range of willingness to pay values. At threshold values of £1000, £10,000 and £20,000, the probabilities for cost-effectiveness were estimated as 1.3%, 1.1% and 6.1%, respectively. This means SWIS had a low probability of being cost-effective.