I just dont want to wake up to people screaming in my face, says michael. i want to have a normal life.

To avoid the stress of early morning wake-up calls, he keeps a strict routine, leaving the house at 6.24am to join a group of other teenagers, most of them black like him, not far from the entrance to belmarsh prison. a haphazard queue forms. gossip, video clips and dance moves are exchanged. by 6.30am, the bus departs.it is hired by local parents to carry kids from one of the poorest parts of greenwich, a south-east london borough, to some of the most high-achieving grammar schools in the state system, in bexley and kent.

In 2016, when the conservative government announced plans to expand selective schooling in england, critics questioned the role they could play in creating a more meritocratic system. the same year, a study from the education policy institute cast doubt on the idea that grammar schools which, unlike other state schools, may select pupils based on academic achievement promote social mobility.

That doesnt stop parents such as michaels wanting to send their children to selective schools. michaels maternal grandparents are from nigeria and his father was also born there. another nigerian single mother in south londons thamesmead, with a son at grammar school,said that for two years she had devoted much of her small monthly income to twice-a-week tuition for her most academic child. a mum from ghana explained that the financial burden continued once her daughter earned a place at a kent school because the uniform cost hundreds of pounds on top of the transport costs.

The headteacher of michaels primary school says up to 30 pupils sit entrance exams for selective schools each year about 13 win places at grammars or independent schools with scholarships. the exams are particularly popular with parents of african origin, she says.

The national average of grammar school students who identify as of african origin is 4.3 per cent. in kent that rises to 5.3 per cent, compared with around 2.1 per cent in the countys non-selective schools. for the borough of bexley the difference is even more pronounced: the average percentage of african-origin students in grammar schools is 20.2 per cent, versus 16.4 per cent for non-grammar schools.

Overall, data from the sutton trust highlights that selective schools dont take their fair share of children from lower income groups. the trust has called for more outreach work by such schools and for the government to provide 10 hours of free tuition to exam candidates.

But natalie perera, executive director and head of research at the education policy institute, says that grammar schools are not the vehicle for broader social mobility. the real difference is made in the interaction of education, home life and wider social forces, she says. policies that promote a healthy start in life for both children and their families, alongside inclusive school environments as well as efforts to alleviate poverty and create safe neighbourhoods can all contribute to narrowing the gap.

Experts also point to cultural heritage and parental influence as factors that give some groups an advantage. kids from low-income families in almost all minority ethnic groups are likely to do better at school than their white working-class counterparts, and are also more likely to get into a selective school.

Michael and his friends arent able to enjoy all the extracurricular benefits grammar schools offer. they must be back on the bus at 3.30pm so he misses out on after-school activities but he does take part in activities and athletics clubs at lunch. the schedule is tough and there are trade-offs even for the academically gifted. michaels mum sums it up: if you have to push and push your child, then a grammar probably isnt going to fit.

For most working-class children, who have little or no choice about their secondary education, access to grammar schools is irrelevant. but such schools may play a role in producing high-achieving role models and, in that regard, have the potential to make a difference. and, despite the best efforts of researchers, it is impossible to calculate the true value in a group of black teenagers queueing outside a prison defying the odds.