@RancidRuby sure...an ability to use initiative, solve problems, take responsibility for personal organisation, way beyond what ordinary teens do...most long suffering parents will eye roll and pick up the dirty laundry so they won't have to deal with a last minute crisis. The matron of a boarding house won't do that. The kid will go to lessons in kit, receive a sanction and get organised next week for laundry day.
Organised prep sessions every night with no phones allowed and staff available to help with difficulties.
Older students organise additional study /revision sessions after dinner
Access to sports facilities to allow gym/swim after work is done.
Ability to form respectful but friendly relations with boarding staff
Taking on "big sibling" roles with younger students, encouraging them to participate and take their share of duties
I have no doubt you'll come back with lots of ways in which day kids and their parents can replicate all that and that's fine, but I've worked in boarding schools now for a long time. There's so much ignorance displayed on this thread it's really depressing. The idea that it might be fantastic for some kids is fought against so hard but I've met dozens who actively want to board, ask to when they live near and could be day kids, ask to so they'll work more, ask to so they can do late and early sports sessions. Loads of benefits for kids who want to be there, and you'd be surprised by how many do.