Cross-sectional associations between lunch-type consumed on a school day and British adolescents' overall diet quality.

•Assessing overall diet quality rather than individual micro/macro nutrients is needed.•Students purchasing lunch from a shop/café have the lowest diet quality score among both age groups.•Packed lunches were the most common type of lunch consumed during a school day.•For older students, packed lunch consumers had the highest overall diet quality, unlike younger children in primary school.•The food environment and student preferences have an impact on adolescent food choice.