I certainly believe that children in the top 15% should go to academic schools. Those schools my children went to like that are in no way pushy or crammers or for what I term properly gifted but they are suitable for bright children who tend to do better in them. Sadly in most of the country you have to have a spare £8 - 10k a year after tax to be able to buy that for children unless they win a scholarship.
None of mine are quirky/eccentric bus timetable types, just average in the class in these academic schools and as teenagers more interested in socialising than work although they still mostly got As at A level like most people in those schools.
But now in my 40s and seeing how people I know have turned out in life how many exams you passed is by no means the most important thing in terms of success financially in life or even looking at my 3 at university - getting jobs - it's not who has the most A*s, it's whether you get on with the person interviewing you, whether you have social skills, can talk, are shy or not shy etc etc once you've met the basic good A levels and 2/1 degree from somewhere decent.
My sister's child will be better at the school he has just won a place at, without doubt because there will be other eccentric children there, there will be high performing dyslexics and also at 6 who knows what he will be like. He may change completely in the next few years.
I don't think moving up a year is always helpful although I was a year young at school and was 17 when I went to university. That was fine - one year because I was quite mature but more than that just makes the child not fit in. My brother was a year young too.
As for round pegs, all 5 of my chidlren are very different from each other and I like those differences. Some are more sociable than others and what I always aim to do is make them accept that child X isn't better than sibling Y just because one has 100 friends and the other 1 or whatever. It's just a difference. However they all benefit from some degree of learning how to behave with others, how to give talks, how to socialise, smile, look people in the eye, not make a fool of yourself, wear the right clothes. For some that is easy and natural. For others that is much harder. My own twins, one is much shyer than the other but cleverer and better at school. They had to give a talk to the class recently. The shy one found that much harder than his twin did.
If I had a very quirky child I would I suppose try to teach it what isn't a good idea (assuming it doesn't have some real special need rather than just being borderline aspergers or just a bit unusual) in terms of behaviour. I would aim to make it emotionally robust and try to find some hobby where it could excel. Becoming good at sport often really helps in schools for example - the nerd who does body building and ends up school champion is common in story lines because it can work as a tactic. Or just finding your niche at school with the outsiders can work too.