Sorry to interject, but schools do *not* have to select solely on cost.
Schools have several routes to purchasing things like catering - for example using frameworks:
https://buyingforschools.blog.gov.uk/2023/05/25/a-beginners-guide-to-using-frameworks-for-school-buying/
That allows them to select on exactly what they value - which might be cost, or quality, or variety, or SLA etc
https://www.gov.uk/guidance/find-a-dfe-approved-framework-for-your-school
Undoubtedly some schools do go for the cheapest - but they can fire their caterer if they don't perform to standard.