Please can someone answer this simple question about state selective schools?

What you get at selective schools is a type of indirect social selection. This produces a peer group which is very different from its non-selective equivalent, both in terms of its behaviour and its academic/life expectations. As a parent with a girl at a selective, this is very important to me, especially after I worked in non-selectives and saw the reality on the ground for myself.

The anecdotal examples are startling. My daughter was not the brightest at her local state primary, but ended up at a selective whilst almost all her primary schools mates are at comps. Four years on, there is no comparison between what she is attempting and what they are, both academically and culturally; what the others get up to and how they behave generally are also very different.

This borough, Barnet, has three selective schools, with a total capacity of around 370 kids per year. All three schools accept pupils from other boroughs, including some who move from other parts of the country. Even setting aside the notorious reputation of education ‘achievement’ statistics, I wouldn’t expect much of an impact at a borough level.

But ask any family around here and they would love their kids to attend a selective.

Comparison between selective and non-selective education is complex. Pupils do move across LA boundaries so around 20% of grammar school pupils come from outside the LA. For some LAs this is as high as 75%. And there is evidence that grammar school pupils generally take harder qualifications than more able pupils in non-selective schools, so a straight comparison of grades is potentially misleading.

There have been a lot of studies adopting varying methodologies. In broad terms most of them show a small positive effect on GCSE grades for pupils attending grammar schools, with results up to a full grade higher than pupils of similar ability at non-selective schools.

The effect on pupils failing to reach grammar school is more problematic. Some studies report a small negative effect, others suggest no effect. I haven't seen a study that suggests a positive effect.

Some supporters of selection at 11 suggest it improves social mobility. There is little evidence to support this in the studies I have seen.

Well, you're obviously begging the question as to whether it is a good idea, at all.

Perhaps you could answer this question. Are outcomes worse in wholly selective authorities (overall)?

Also, are there any truly wholly comprehensive authorities, or do, in fact, most "comprehensive" schools actually set for many subjects?