The Conservatives would give head teachers more power to improve school discipline, David Cameron has said.
The Tory leader, speaking to a support group for troubled school-leavers in London, said heads should be given the final say on exclusions.
Students that are excluded should be given more help, he said, to combat a growing divide between children from well-off and deprived backgrounds.
"It seems to me absolutely clear that we have to give the head teacher the ability to decide who can and who can't attend their school," he said.
"Heads must feel they are the captains of their ships and in charge of their school."
He said increased powers for head teachers should be combined with more support schemes for the socially excluded, and proposed contracts between parents and schools setting out how students must behave.
He went on: "The problem in the country today is there is a gap between those children from the most deprived backgrounds and those children who have a good start in life.
"That gap is getting wider and it is a huge problem for our country."
