Complex sentence: Fiona Twycross has been campaigning to persuade the Labour Party to commit to the universal policy on the basis that according to the Institute for Fiscal Studies and the National Centre for Social Research free school meals for all significantly increased attainment in schools.
Split into simpler sentences: Fiona Twycross has been campaigning to persuade the Labour Party to commit to providing universal free school meals. She argues that according to the Institute for Fiscal Studies and the National Centre for Social Research, free school meals for all students significantly increased attainment in schools.