Official figures show hundreds of primary schools are failing to give their pupils a decent education in reading, writing and arithmetic.
Data released today shows England's best and worst ranking primary schools based on performance in this summer's national curriculum tests.
It's thought around 800 children in the capital still without primary school places, leaving parents concerned.
A Department for Education spokesperson said:
We know that London has pressures, which is why we’re creating thousands more places to deal with the impact of soaring birth rates on primary schools.
We've already invested just over £1 billion in London this year and last to create extra school places and hundreds of millions of pounds will follow.
We are building Free Schools and letting the most popular schools expand to meet demand.
We are also intervening to drive up standards in weak primaries across the capital, which have empty places simply because parents don't want to send their children there.
This year, parents of 100,000 pupils living in London applied for primary school places.
78% were offered their first preference school. 90% received an offer at one of their top
Number of children across the whole of the London that secured their:
First Choice: 78.72%
Second Choice: 8.31%
Third Choice: 3.54%
6,220 children didn't get any of the top six choices of Primary School.
Number of children that secured their:
Fourth Choice: 1.67%
Fifth Choice: 0.91%
Sixth Choice: 0.63%
More than 20,000 children have failed to get into their first choice school in London
That means that two out of ten children starting primary school in September will not be going to their preferred school.
In total, 6,000 children missed out on all of their school choices, either because their parents listed only one school, or because of huge demand for the six they chose.
Of those, 4,700 have been offered a place at an alternative school and 1,500 currently have no place. Parents in this situation will be advised of their options by their local authority.
The Pan London Admissions Board says that there is unprecedented demand for primary school places across London.
A total of 100,000 children applied this year - an increase of 6,000 since 2011.
Chairman Helen Jenner said: "It is important to emphasise that although the system is very efficient, it cannot create places at schools which are already full and not all parents can be offered their first preference.
"London local authorities are working hard to try to ensure that they can offer every child a school place but with this surge in demand it is becoming increasingly difficult.”
Kensington and Chelsea is at the bottom of the table, with 35 percent of children missing out on their first choice. But Tower Hamlets came out on top with only 14 percent being disappointed.
Families will find out this evening if their children have got into the primary school of their choice.
A surging birth rate in the capital means that there aren't enough places - and thousands are likely to be disappointed.
This week London Tonight will be showing the first in a series of special reports, looking into the shortage of primary school places in London. We'd like to hear from you if you or your family are likely to be affected by it.
Are you a parent, with a child due to start school in September? Are you worried about them getting into the right school? Let us know your thoughts by email - and please include a phone number - by writing to firstname.lastname@example.org.