Hi Saisanne. This thread seems to have gone very negative, so if it's possible to pull back from that, and go back a couple of pages to where posters were giving very good and supportive advice, I think that would really help.
I have a DD who has just turned 4. She is very advanced - she's now reading chapter books, is very skilled in maths (which she's picked up completely herself, getting as far as multiplication on her own), she's exceptionally articulate, bright, cognitively well advanced for her age. She's also lucky in that both DH and I were also both gifted/talented kids ourselves, and now both work in very high profile intellectual professional jobs, so we were kind of expecting that DD might be very bright, and she is. She's lucky in another way in that as well as having our experience to support her, she also goes to a nursery that has a lot of children in similar positions (a lot of our work colleagues have children at the nursery), so she's surrounded by children who often are also reading, very bright, have academically able parents, and so on. We aren't wealthy by any means, but I won't kid you that there is a social advantage there: my daughter is at nursery around bright children of bright middle-class parents who know how to relate to bright kids. She gets an advantage from that as she isn't markedly different to the skills of the others, though she's clearly amongst the brightest. But because of this, DH and I are intensely relaxed about her doing any kind of academic learning at nursery. We'd just rather she played and occupied herself running about and doing all the things we can't provide at home as we have a tiny flat - messy play, outdoor play, painting, social interaction, etc. - and, to be honest, we're just glad someone else is looking after her while we're at work 
I don't know your background, so I may be completely wrong in this: but it strikes me that you seem to feel that you're at sea here and have been doing a lot of research on gifted children to try to provide something you think your DS is missing out on. Yes, if he is in a nursery where he stands out as unusual to the other kids then you might worry that he isn't getting something vital. However if there are 60 kids in his session, then statistically there are going to be a few who are just as smart as him or nearly so. And in any case, why do you want him to be challenged and stretched at nursery? Honestly, the social skills and the experience of play are far far more valuable at this stage in his life, and will be for quite a while. He doesn't need academic stretching and support at this stage. Just answer his questions, tell him stories, and allow him to learn how to interact with other children. Let him run about and have loads of sleep and try out physical activities (and don't overwhelm him with classes). Play him music and read him stories - not those awful Biff and Kipper reading scheme ones, but proper ones, fairy tales and Brambly Hedge and Enid Blyton (the young kids' ones like Brer Rabbit and The Wishing Chair...)
Honestly, I'm speaking as someone who was G&T myself and on behalf of my DH. He had a mum who noticed he was gifted, didn't really know what to do about it, and so did a lot of "research" and took him to child psychologists and accelerated him in schools and took him out of schools and enrolled him in special tuition and all sorts of stuff. It messed his life up to the extent that he'll never, ever recover from it and has lasting, significant emotional problems from being treated like that and not ever being able to form good peer group friendships. Honestly, better that your little boy doesn't quite get "challenged" academically but has a good time playing in the sand pit and learns how to make friends with all different kinds of children than always feeling the odd one out. It is not nice for a clever kid to feel different and singled out, because there is a lot of low self-esteem and emotional pain waiting for him in the "specialness" of being different. Please hold off on this as long as you can.
Anyway, children can't tell how bright their peers are with any reliability until they are at least at secondary school. Honestly - it's true. Don't encourage him to feel himself different to others or that his peer group aren't up to his standard - it's a recipe for loneliness.
There are a few things you do really need to know if your little boy is very bright.
- The best thing you can learn, straight off, is that the whole "gifted and talented" business is a race you can't win. There will always be someone else's kid who is brighter and quicker than yours - an IQ that is higher, a child who has better musical talent, parents who are richer or have better cultural capital and so can give their child an advantage. You only harm your child by getting into the race - your kid might be a thoroughbred but he can't win the National every time. And someone else always has posher stables.
- There is a lot of charlatanry out there. There are private educational psychologists after your money, special tutors who are on the make, gifted child courses that cost a fortune that tell you they will endow your kid with special abilities, Mensa-style clubs making money out of flattering people about their IQs. None of these will ever do anything for your child's real future. Try to trust the teachers at the nursery and school - you are not paying them so they don't have to flatter you, and they are the ones who will be working with your child each day. If they are telling you that he has needs he has to work on in social development and behaviour, it is important to know this.
- Relax! A really bright kid will still be bright even if they don't get "challenged" for a while. I spent a lot of my primary school career loafing and refusing to do anything. I had a reading age of 16 at 6 and refused to have anything to do with the reading scheme; similarly with maths. It didn't make one iota of difference to my academic achievement at 18/21+. However, I did completely fail to learn good work habits and any form of self-discipline, which would have real helped a lot in my life. Make sure your kid knows that sometimes you just have to jump through the hoops, even if they are too-easy-for-you hoops, and that's OK. And sometimes you do have to cope with not having a great teacher who gets you, or not being perpetually stretched, or feeling like you're not appreciated. And that's OK too; sometimes you also have to get used to making your own amusement, or learning how to be productively bored, or doing things just to be a good citizen, or getting perfect at something through hard work rather than dashing through it. And it's OK for a bright child, even a very bright child, to be pottering about in a mediocre primary school with parents who aren't frantically looking up Suzuki violin and private tuition and how to get their kid into a London day prep on scholarship. (Because frankly that's a grim life, too, and if you were a billionaire your child wouldn't necessarily be any better off being crammed through the London private tuition and prep circuit and being force-fed every stretching experience on offer.) Just let him be himself for a bit and relax about his academic achievements and abilities. And I know everyone else on this thread has been saying this, too, but as a former "gifted" child, I can tell you that it's absolutely true!