Children in England may be starting school too young and face a system "uniquely" obsessed with high-pressure tests, research has found.
Pupils take more tests and attend larger primary schools in England than in many other countries, reports from the Cambridge-based Primary Review concluded.
There is little evidence that making children start school younger improves their education, according to the research, which forms part of the biggest inquiry into primary schooling for decades.
A report by Kathy Hall, from National University of Ireland in Cork, and Kamil Ozerk, from the University of Oslo, found that tests in England were "high stakes".
But this pressure could undermine the aim of testing pupils to help assess their development and what they need to improve.
"What distinguishes assessment policy in England is the degree to which it is used as a tool to control what is taught, to police how well it is taught, and to encourage parents to use assessment information to select schools for their children," the report said.
"England is unusual in its high incidence of assessment and is exceptional in its emphasis on statutory external standard assessment for children at ages seven and 11."
The researchers compared primary education in the rest of the UK, France, Norway and Japan to isolate "the uniqueness of England's assessment policy".
A separate Primary Review report, from Anna Riggall and Caroline Sharp at the National Centre for Educational Research, questioned whether pupils start school too young.
The study said: "The assumption that an early school starting age is beneficial for children's later attainment is not well supported in the research and therefore remains open to question."
