Teacher here. I publicly and privately criticise grammar and private education. Don’t presume to speak for all teachers.
Your comments are reductive and often inaccurate. The idea of some ‘sink’ schools only facing a handful of children ‘bright enough’ to get a few 6s is a completely back-to-front way of thinking. What constitutes a ‘bright’ pupil? Someone with sufficient privilege to have gained a good grounding in knowledge and skills within and beyond school, making it easier to accelerate progress? Someone with a sufficiently stable home life to have the emotional self-regulation to be able to behave? Someone with parents who value education enough to instil that value in their child?
At what point is a child considered bright and, conversely, when do we write them off because they’re just not bright enough? Is it when they show sparks of potential before their home life goes down the drain? Is it just a shame, but never mind, when they fail the 11+ because of this? Or, within reason and allowing for some innate natural variation, is ‘bright’ mainly just a product of the multifaceted privileges I’ve described?
There are many pupils in what you call ‘sink’ schools with the potential to get far better outcomes than they do and under-achievement is a product of complex socio-economic circumstances that go far beyond school. Well-run comprehensive schools can and do support good pupil progress - you may know that state schools have recently started to outstrip private schools in England in rates of pupil progress from starting points. Nonetheless, there are multiple factors outside of schools’ control affecting achievement at every stage that require wider societal reform and much better funding of more comprehensive services. Thinking of children in terms of ‘bright’ and ‘not bright’ is incredibly simplistic.
Equally, there is very little evidence that grammar schools did/do much for social mobility overall. They largely took/take already privileged children, usually those with some of the ‘protective’ factors I’ve outlined which made them more likely to already be on track for success by 11. There’s no evidence base that these children would’ve been less successful in comprehensive schools, and nor could there be - because they went to grammar schools and it’s their outcomes there by which we judge those schools. Equally, there’s evidence (e.g. Institute for Fiscal Studies) that the trade-off for pupils not getting into grammar schools in grammar school areas is slightly worse outcomes than their comprehensive school peers.
Survivorship bias is useful in understanding why we often over-attribute success to the grammar school system. Look at the work of Hungarian statistician Abraham Wald to help with conceptualising this.
You’ve also mentioned behaviour in secondary moderns being better than in some comprehensives today. I’m unsure what your data set is for that, but this seems to be another example of oversimplifying a complex issue. Taking just one aspect of this, there’s evidence about the decline of authority-based relationships in which context it would be expected that behavioural standards would now be harder to uphold in all schools than they used to be.
Grammar schools might be an appealing option for parents who (understandably) want to feel their child is in the best possible environment, but they’re not the answer to the issues with our education system or wider societal inequalities.
Lastly, you are criticising some posters for needing to lighten up (I paraphrase). You’ve asked a very serious question though, so you should expect serious answers. Most teachers work very hard, and many in challenging circumstances. When people fight to improve life chances for disadvantaged young people, then offer you thoughtful responses borne of years of experience, and provide supporting evidence, it’s advisable to at the very least listen to them rather than taking the inaccurate, simplistic and patronising view that all state school teachers would secretly want to privately/grammar-school educate their children if only they could afford to.