The poorest people are losing out on places at the best primary schools in England, research suggests on the day parents receive news of allocations.
The least wealthy families have less than half the chance of the wealthiest of sending a child to a top-rated school, analysis from Teach First says.
The teacher training group adds poorer families' children are four times more likely to be at weaker schools.
The government says many more pupils are now in good or outstanding schools.
The claim comes as councils say they will need 336,000 more school places by 2024.
And as the crunch in primary school provision intensifies, council leaders in some areas say the scramble for places at good schools is even more acute.
In Milton Keynes, where there are twice as many pupils going into reception as will be leaving sixth form, council leader Peter Marland says his officials are working hard to keep pace with demand.
It is one of the biggest areas for house building in England, so schools are being built to cater for the occupants of new housing.
But, he says, these schools are fast being filled up by children already living in the city, who cannot get a place nearer their homes.
Cllr Marland says not only are more children travelling further to take up school places, but those from less affluent backgrounds are at a disadvantage in an increasingly complex admissions system.
He says: "Unless schools, or someone, steps into coaching the poorest families on admissions, then it's those from affluent backgrounds that will get the good places."
Teach First analysed data on Ofsted rankings for all schools in England and mapped it against the areas with the poorest children living in them.
The report explains that schools serving poorer communities are less likely to be rated good or outstanding as they face more challenges because of the nature of their pupils.
This means that families from such areas can find it difficult to get places in highly-rated schools.
Teach First suggests recruiting more highly qualified teachers and school leaders in these areas could be a solution.