Tens of thousands of extra school places will be needed by next year amid a continuing surge in demand, the Nation Audit Office said.
Ministers will visit schools in London today to see the problem for themselves.
According to Barking Council, an estimated 1,000 extra primary school places will be needed in Barking each year, in line with projected population growth.
More top news
The Facebook boss reacts to the detail found by the investigations of The Guardian, The New York Times and Channel 4 News.
Sunshine in short supply
A man has died after his head was crushed in a freak accident involving an electronic seat at Vue Cinema in Star City, Birmingham.