Some 2,000 new summer schools running across England will attempt to put 65,000 poorer children on an "equal footing" with their wealthier peers, Nick Clegg said today.
The deputy prime minister said the "brain training" camps would help struggling primary pupils make a good start at secondary this September.
The schools are being funded by £50m targeted at disadvantaged pupils.
They will focus on literacy and numeracy, and art, music and sport.
There will also be sessions to help youngsters get to know their new teachers.
About £50m has been made available to schools through the "pupil premium" - extra funding for disadvantaged children - to run the camps this year.
Mr Clegg said: "This is £50m worth of extra brain training giving tens of thousands of disadvantaged pupils a flying start at secondary school.
"It's two weeks in the summer holidays where pupils can catch up on learning and get to grips with life in secondary school - in short, get in the starting blocks ready for the off in September.
"Those who struggle to make the transition are often among the poorest in society, but two weeks of activities can really help to bridge the gap.
"It's good news for mums and dads too - no parent wants their child to be left out and fall behind. But not everyone has the luxury of taking long periods off work during the summer break.
"Summer schools will ensure pupils from disadvantaged backgrounds can start secondary school on an equal footing with their peers, setting them up to succeed."
Many pupils find the move to secondary school daunting, which can lead to a dip in their performance that they never make up, according to the government.
Its research shows students eligible for free school meals regularly under-perform.
By the end of primary education, just under 58% of disadvantaged pupils have achieved the expected level of attainment, compared with almost 78% of other pupils.
Children's Minister Sarah Teather said: "Many pupils, often those from poorer families, suffer a dip when they join secondary school.
"These brilliant summer schools give those children that need it a head start and the extra help they need so that they are well prepared to succeed at this crucial stage of their education career."