The data protection act generally requires personal information to be gathered and used for specific purpose. School records are not gathered to pursue benefit investigations:

> The DfE said the data-sharing agreement was “designed to provide confidence that the right and fair amount of benefit is being paid to the right claimant and any children included are benefitting”.

They were unable to provide further detail beyond what is in the data-sharing agreement to “ensure we balance transparency with protecting its capabilities by not tipping off fraudsters about how it tackles fraud”.

https://schoolsweek.co.uk/revealed-secret-deal-to-let-benefit-fraud-squad-snoop-on-pupil-data/