I looked at your post, but didn't reply because I felt that all that can be said is pure speculation. Your DC's score is impressive! My boy scored 237, which I suspect will put him just below the cut-off score, as the last few years that seemed to be between 240 and 245.
I would therefore think you have absolutely no worries. We are hoping for a grammar school place, as he passed them all, but even then you never know... Graveney was our plan B.
Graveney is excellent, and, even if there are 70 kids with a higher score, there will be quite a few who will be going to the grammars, allowing lower scorers in, even on the waiting list. But, as I said, with your score, I would think you will be fine. Bolingbroke is nice enough, but, with no Sixth Form yet, it seems a little scary if you child is very academic.