Do not worry about a day pupil at a boarding school. They have the same friends and it is not a problem.
Maybe, maybe not.
I was a boarder at a school that was about 50:50 day and boarding pupils and there was very little overlap. We shared lessons with day girls, but most of the big bonding experiences were separate (partly because the house system comprised several houses of daygirls only and several of boarders only), especially weekends.
At recent reunions (in real life and on Facebook), several people have observed how different were the experiences of day and boarding pupils.
It's also noticeable that most of the boarders have stayed in regular touch with several boarding friends over the last 20+ years, whereas most of the daygirls had lost touch with most of all of their day friends.
Of course my experience may not be typical, and it was a generation ago, but I would be wary of being a day pupil in a school that was predominantly