I do not see why grammar schools , should only been seen as acceptable for 'genius' pupils. I have been looking at the Northern Ireland Grammar schools and it seems to me they have got the system right!
you do not have to be 'genius' to get in , nor not achieving '5A*' GCSEs does not deem you a failure. However, perhaps more relevantly the requirements for admittance to the 6th form in Northern Ireland's grammar schools are achievable for most hardworking pupils.
This is important because it means even if you fail the 11+ there is a real opportunity to get there if you want to !
A Grammar school education is not 'cut' off from any student in Northern Ireland . This is different from the 'highly' selective grammar sixth forms usually found in England.
This means that as some posters remind me a grammar school education in England is also unavailable at 16 as well 11 for failing the 11+. This is due to the stringent academic requirements for entry to sixth form at English grammar schools.
This having been brought on by 'Supply and demand Economics' of the limited supply of grammar schools.