"... because they're thick"
Hmmm. Certainly not a view you'll see often in an Indie column.
When it comes to nature/inheritance vs nurture/culture in all its different guises, IMHO its a case of more or less, not either/or. From just looking around, it's likely that to an extent bright parents will have bright kids and vice-versa - yet we all know bright parents with not-so-bright kids and not-so-clever ones with clever kids. You see this as a parent and governor. And as a governor it's wonderful to see a child from a poor background who shines like a star in the classroom, and makes you think 'there's no limit to what this child can achieve'. That feeling must be doubled and redoubled if you're his/her teacher.
But of course there may be limits. If that child goes to a dreadful secondary school, or starts to hang out with the wrong crowd at adolescence, all that potential may be unfulfilled - and I'd have thought that would break a teacher's heart.
Which is - or was - where grammar schools came in. A hundred and fifty years or more ago, class determined your future and only a determined or fortunate minority of the poor could succeed. I don't know if anyone did the research, or how they'd do it if they did, but you'd assume that intelligence was spread much more evenly over the whole population. Certainly the great Victorian flowering of autonomous working class institutions, from the trades unions and friendly societies to the Co-Ops and clubs, triggered by mass literacy, supports that idea.
Free education, grammar schools and university grants changed all that - although as late as the 1930s poverty in its purest sense was still holding children back. My mother had to leave school at 16 to help bring money in, despite being a very bright student. I look at her school notebooks and her teenage annotations in her prize copy of Palgrave's Golden Treasury and marvel at the high educational standards prevailing in a Welsh grammar. She only made it to teacher training college after the war, on a grant given for her war service in the WAAF.
I'm sure someone must have argued by now that the grammar schools moved a lot of working class children into the middle classes, and that a chunk of the reduced social mobility is down to the cleverest having been already taken. Yet while there may be some truth in that, I still see a lot of bright kids from poor families who I know would do much better in a grammar than a comp. So what if there are a lot of middle-class kids there ? And the point is that while there may be a hereditable component in intelligence, it's only one factor - chance or things we don't know about yet also play a part. The supply of bright kids from ordinary working families is in no danger of drying up (as long as we continue to have kids, of course - another topic). It's the supply of bright, well-educated kids that worries me.
UPDATE - a couple of links I forgot to mention :
Assortative mating - see this by Arnold Kling and this by David Brooks. The irony is that feminism may have increased inequality, as high-IQ females in high-status, high-income jobs choose high-IQ partners in high-status, high-income jobs.
Middle-class IQ - Bruce Charlton (note the idiotic and dishonest comments by Education minister Bill Rammell) and Chris McManus (note ditto by Health minister Ben Bradshaw and the Telegraph headline writer, who should be sacked)