I think if you don't live in an area with depressing primaries, you can't understand the very awful depths they can plumb.
In my job I visit several local primaries a week, many of them are just benign holding pens, fighting against a tide of parental apathy and in some cases parental ambivalence to an education system that will allow their children to read and understand any language, especially english.
I work with children who are not SN and who cannot read anything but baby board books (in any language) at the age of 7 and 8. One of the schools in which I work has display boards so bad that my fingers itch to correct the TEACHERS' explanation panels. The children are often from very deprived homes and because it is a high rental area there is a turnover of 80% of the children from reception to starting secondary. 80% of the children also do not have english as a first language, and with the best will in the world, the teachers are never going to be doing anything but playing catch-up.
The thought of sending any reasonably intelligent child into a situation where they will be mostly ignored by the teachers, (because they're too busy with children who need a lot of help), with no playing field to expend energy on, and an apathetic parental force who won't help in any way fills me with dread. And it's disingenuous to pretend that only academic considerations are important with a very young impressionable child.
For reasons that I won't go into we cannot move, we have no choice about where we live, and if I could afford private primary eduaction for my son I certainly would. As it is we may well have to home-school.
I moved from an area with excellent primary schools when my older son was 8, he didn't do well in his new school here, we ended up home educating him for the last year of primary, and practically bancrupting ourselves to pay for a state grammar boarding school at 14 after a disasterous, brief, secondary, state educational experiment.
The practical considerations are enormous, we can no longer afford a car, the roof is leaking and we've removed the gas central heating system because we couldn't afford to maintain it. My OH has been jobless since DS2 was born so there is little hope of a financial revival.
Did we do the right thing by sending DS1 to boarding school? Absolutely!