From the perspective of new parent at Pate's (DD1 yr7 - loving every minute!!
) - I have to say that the school themselves really integrate next year's intake from now, making them feel a real part of the school before they even start. Personally can't fault the pastoral care and sense of belonging, right from Allocation Day, so as others have said, hopefully your DS will feel more comfortable about his excellent achievement after Wed. By the time September came round DD had already started referring to Pate's as "my school", had met up with her classmates several times, and was familiar and comfortable with the layout and procedures at school, and from what I gleen from other DCs, the same is true across the board.
Pate's intake is so vast that the majority of children won't know more than a few people. I seem to remember Mrs Blackwell saying current Yr7 came from 93 primaries - much travelling and many visits for her in June/July as she tries to see all new pupils. Senior school is such a huge change for them, they're bound to be uneasy (not to mention how you feel as a parent!!
) - keep calm, keep reassuring him, reinforcing his fab result!