This policy is still being implemented by the government. Parents can apply for free school meals for Children in school above year 2 and may be successful if they receive any of: Income Support, income-based, Jobseeker's Allowance, income-related Employment and Support Allowance, support under Part VI of the Immigration and Asylum Act 1999, the guaranteed element of Pension Credit, Child Tax Credit (provided you're not also entitled to Working Tax Credit and have an annual gross income of no more than £16,190), Working Tax Credit run-on - paid for 4 weeks after you stop qualifying for Working Tax Credit - and Universal Credit.
Category: Social and Welfare
Source: Manifesto - Page 52
Reference 1: Applicaiton for free school meals