Sancton Wood, St. Faith's Cambridge and other independent schools

[DknyQueen]

Hi everyone,
I have name changed for this to avoid being recognised!
DS1 is in Yr 6 attending a primary school in one of the villages around Cambridge. He's working slightly above average for his year group but he is very lazy and I fear the school has not taught him the meaning of working hard. We have discussed the possibility of applying to a private school with him and he seems keen to give it a try but not so much to put in the extra work needed for him to pass the exam! Because of the way he is, my DH and I agree that he would benefit from attending an independent school but one that is not too competitive at least to start with. For this reason we have ruled out The Leys and The Perse, apart from the fact that he would probably not pass the exam anyway!
We would like him to attend a more "nurturing" kind of school where he can be gently taught to work hard and take pride in his achievements, ideally one that has small classes and that is academically focused. We are considering Sancton Wood, St. Faith's and the King's School in Ely although the latter would be our least favourite because we don't fancy moving to Ely!
Can someone recommend either of these schools and tell me what the ethos is like and whether you think a bright but lazy 11-year old would thrive in such environment? Have we got any other options?
We are open to all suggestions and comments. Please fire away!
TIA