We're friends with parents of a child at nlcs because she left our state school to go there at the end of year 2. We have nlcs down for 11+ but from what we now know we think either the school is not really ahead of others in terms of school work or the child is too bright for them.
Hampsteadmum, they don't do year 4 work or use yr 4 book at year 3. I KNOW that because we regularly see their year 3 work and I can even tell you what they are doing right now in maths.
For Lilly2013, don't worry about the home-work level (it is not too much and not too difficult for any child at that stage in a good state/private school), don't worry about the HIGH intensity teaching (if it's there at all, it is not far away from anything they do at most good schools), and as for rich parents (don't even think about that although the father of the child we know is something special brain-wise and will sooner or later appear prominent in national life).
What I like of nlcs is the array of outdoor projects they expose young pupils to in addition to their studies. Yesterday for example those in Y3 learnt about Vikings and had time to research and prepare for this class and seeking objects to take to school. My state school child was filled with envy but she did most of the preparation with her friend but could not appear in the class with her good friend and had to wait for her from school to fill us in with the rest - which they then practised together.
This is where nlcs develop the child and prepare them for outstanding results in later years. They have outstanding scripts for the child to learn every now and then. They hold several events every now and then. In less than one year, we can see the difference in the all round ability of the nlcs child rather than us just knowing her as being very clever.
So if you believe that people learn more by doing projects, testing things out by themselves and being regularly creative and challenged to think outside the box rather than being taught to memorise stuff or just do kumons worksheet forever, then you would easily understand why nlcs appears to be a great school. This is what I think separates them from the other schools I know about and why they produce outstanding results. They have the right formula and work really hard on presentation too. If I was in government, I would get some of their people to help out on education policy.