Schools are segregated along class lines, leaving the poorest children struggling to achieve against poverty and deprivation, a teacher's leader warned on Wednesday.
The union head said stratified schools are "toxic" for deprived youngsters as it means they fail to learn important qualities such as aspiration and effort from their richer classmates.
It is the coalition Government's "dirty little secret" that their education cuts and reforms are making the lives of the poorest children tougher, Dr Mary Bousted, general secretary of the Association of Teachers and Lecturers (ATL) suggested.
And she raised concerns that schools are held up as the scapegoat for educational failure, accusing ministers and Ofsted of "seeking to wash their hands, like Pontius Pilate" of the problem.
In her speech to ATL's annual conference in Manchester, Bousted said: "We have, in the UK, schools whose intakes are stratified along class lines.
"We have schools for the elite; schools for the middle class and schools for the working class. Too few schools have mixed intakes where children can learn those intangible life skills of aspiration, effort and persistence from one another.
"The effect of unbalanced school intakes is toxic for the poorest and most dispossessed.
"And whilst teachers and school leaders strain every sinew in these schools to raise aspiration and achievement, they struggle always against the effects of poverty, ill health and depravation and children in these schools routinely fail to make the educational progress achieved by their more advantaged peers."
Speaking ahead of the conference, Bousted said: "The poorer children get, the more stratified education becomes.
"Middle class parents want to keep their children away from the social problems that are brought in by poorer children."
Bousted told delegates that claims of low expectations in schools are used by government as a "convenient scapegoat".
She said she was not excusing low expectations, but wanted to make a counter charge.
"I am going to argue that the Secretary of State for Education, and his ministers, and his handpicked Chief HMI (Ofsted chief inspector) are pulling a con trick.
"They are seeking to wash their hands, like Pontius Pilate, of all the causes of educational failure over which they, as government ministers, have more control than anyone else.
"In Michael Gove and Nick Gibb's world it is the school, and only the school, that holds responsibility for the educational outcomes of the poor. If the poor don't make as much progress as the rich, it is the school and the teachers within it who are to blame.
"This, as you and I know, is a nonsense. It is a lie which conveniently enables ministers to evade responsibility for the effects of their policies."
Bousted argued that "this coalition government's attacks on poor children is a blight upon our conception of ourselves as a civilised society."
She claimed that the government has cut funding for Sure Start centres, scrapped the education maintenance allowance for poorer teenagers, removed protected funding for school meals, cut council budgets and made tax reforms that are likely to hit low to middle-income families.
"This is the coalition government's dirty little secret," she said.
"This is what they have done, to make the lives of poor children, already disadvantaged and demeaned through their poverty, harder.
"So it makes sense for them to divert attention away from their destructive policies. It makes sense to unleash a torrent of criticism at schools and school leaders and staff who work, every day, not with political rhetoric but with pupils' lives, lives which they strive desperately, and with diminishing state support, to improve.
"Of course we need to understand just what the school effect upon educational attainment is, and how it can work most effectively in order to raise attainment for all. We have to do better, particularly for the poorest children who stay stubbornly at the bottom of the ladder of educational achievement.
"But, and this is a big but, we also need to understand what needs to be done in terms of social justice to give all children a fair start in life and a fair chance to benefit from their education."
Inequalities in children's health, wellbeing, diet, growth, readiness for school, access to books and ability to stay in education after the age of 16 are not accidents of birth, Bousted said.
"Schools cannot vanquish these inequalities; they can ameliorate them, but in vastly unequal societies only the brightest will escape the lasting effects on inequality."
A Department for Education spokesman said: "Schools cannot solve all problems. It is clear though, that a lot of schools haven't properly addressed poor performance.
"Union leaders should be challenging underperformance in our schools on behalf of their members, rather than defending a culture of underachievement."