The announcement, in his keynote speech at the Liberal Democrat conference, forms part of the coalition government’s response to the rioting this summer.
"Too many of these young people had simply fallen through the cracks. Not just this summer, but many summers ago when they lost touch with their own future," he told delegates.
He pinpointed the move between primary school and secondary school as a key time for "struggling" young people to go "off the rails".
The two-week summer school is designed to help disadvantaged children get up to speed and prepare for "the challenges ahead".
Clegg added: "We know this is a time when too many children lose their way, so this is a £50m investment to keep them all on the right path."
The move has been welcomed by The Children’s Society chief executive Bob Reitemeier.
"We know from our work with older children that the move from primary to secondary is a critical stage in a child's life that can dramatically affect their future.
"Providing additional support for those children who teachers and parents know will find it hard to adapt to a new school environment could make a big difference by nipping problems in the bud before they escalate.
"This approach makes perfect sense and, arguably, should be provided during their first year at secondary school as well as before they start school."
