Upvote:2
It says "visits with a [...] school", not "visits to a school". It's talking about students at foreign schools visiting the UK as part of their studies, not people who are visiting the UK to study at a UK school. Compare "I am visiting with my family", which means "I am visiting and so are, e.g., my partner and children"; "I am visiting with my school" means "I am visiting and so are other people from my school."