It’s been a while now (5 or 6 years) so things may well have changed, but when my DS was called to interview, all the boys who had applied from his school were contacted on the same day. So interview letters were sent out in blocks. Then he had the same interview slot with the 5 or 6 others from his school. We all (boys and parents) had a talk / Q&A session from the head in his office, then they went off for individual interviews.
They were all offered places, but I think only two took them up. It’s a fantastic school, but many apply from more Central London locations (because they’re are so few boys options at 11 plus), but ultimately decide to take other schools eg Latymer Upper, CLBS or KCS (now that this has a larger 11 plus entry) - in order to avoid being tied to the coach journey for years on end!
None of them got scholarship offers though, so I don’t know how that works.
The other thing I do remember is that DS had a handwritten Christmas card from the head before the exams, wishing him the best of luck. No other school does this!
In the interview, he was asked what his parents did (
), so do make sure they know this! Also, they were asked, “What do you think makes a good lesson?” I do remember this because DS gave a quite “interesting” answer to that one. Another of his friends was asked, “What will you bring to the school?” and he answered “My sports kit and pencil case.” 
Anyway, they must have a sense of humour because both were offered places, through they went elsewhere in the end.
Good luck!!!