Thank you some people have answered my question. I do feel though that there would be a reduction in the 7% using private education , what the percentage would be ?.
I am neither pro nor anti grammar schools, having experienced the best and worst of the system. I do however believe that DD2 and DS are benefiting from their grammar schools in a way that would not be possible (except for the Hert's 'Comps') in a comprehensive school. I have also seen the 5 or 6 pupils in DD1s (year group) modern school who deserved better (an academic education surrounded with other bright children).
DD1s teachers explained they had about 5 or 6 'bright' children each year but the drop off in ability after that was dramatic . The school tried to 'segregate' academically as much as possible the bright pupils from the others.
Hakulyt has numerously posted about how bright her DS is, however he is like my DD1 was ,in the wrong school !. Hak has cited behavioural issues on the minibus going to a school football match. This is just one way that the selective system can destroy bright children by confining them to poor behaviour from children who are just passing time 'academically'.
350 grammar schools would be just over double the current number of 164 and would include a large no of them having a large boarding provision.
The benefit potentially of doubling the number of grammar schools ,would be to reduce the annual 'bunfight'. This would be because there would be enough places for any pupil who might benefit from a traditional structured academic education.
That is the positive side of the 'coin' ,what happens to the rest , it is perhaps greater inequality academically and economically.