The government website (GOV.UK) explains that a child may be eligible for free school meals if his/her parents are in receipt of any of the following benefits:
Children who get paid these benefits directly, instead of through a parent or guardian, can also get free school meals.
Your child might also get free school meals if you get any of these benefits and your child is both:
This does not include all children in Reception, Year 1 and Year 2 who are eligible for Universal Infant Free School Meals. This is a different scheme and parents receiving any of the above benefits must inform the school as the school may be able to receive additional funding.