An award-winning teacher says it is "immoral to the point of child abuse" to make children sit the 11+ exam.
Thousands of Birmingham pupils will take the test in several weeks' time in a bid to get into one of the city's prestigious grammar schools.
But Phil Beadle, the controversial star of Channel 4's The Unteachables and a former Secondary Teacher of the Year, said failure to pass the exam harmed children's self-esteem.
In a thinly veiled attack on Birmingham's King Edward VI Foundation, Beadle also accused grammars of stifling pupils' creativity and claimed the standard of teaching was "less skilled" than at comprehensive schools.
Birmingham has eight grammar schools - six in the city and two in Sutton Coldfield - where selection is by test only.
Last year a total of 2,974 girls and boys applied for 274 places at Sutton's two grammars alone.
Beadle said the system paid "lip service to the notion of social equality" while writing off the life chances of those who were unsuccessful in the exam hall.
Children who sat the "unbelievably highly pressurised exam", and did not get a place, viewed themselves as "a failure at the age of 11".
Beadle said: "I think that is immoral to the point of child abuse. It is going to impact their self-esteem for the rest of their lives."
He added: "You go to these places (grammars) where the only success is eight A*. If you get seven A* and an A grade, then you are a failure.
"This carries over with kids from those sorts of schools for the rest of their lives."
Grammars, said Beadle, were trading on past glories and were "long overdue an overhaul".
He said: "These schools consistently sit at the top of the league tables claiming they are brilliant and, in fact, all they have done is select the 180 cleverest kids in the borough.
"Of course, the 180 cleverest kids in the borough are going to get the best results. Grammar schools' achievement has got nothing to do with the standard of teaching in grammar schools, which is significantly less skilled than the standard of teaching in comprehensives."