Primary school children in England are subjected to more testing at an earlier age than many other Western countries, according to a study.
Children are tested more in English schools
This is mainly due to a system uniquely "preoccupied" with national standards and accountability, it argues.
The Cambridge-based Primary Review's report suggests starting school at the age of five may be too early and questions provision for the very young.
The government says it makes "no apology" for focusing on standards.
The three primary review research reports are robust in their analysis of the current state of primary school education in England.
One key theme is the emphasis on testing and associated publication of results in league tables.
By comparing England's curriculum and assessment policy with those in 22 other countries, including France, Norway, New Zealand and Japan, the authors found a "unique" system dominated by tests and league tables.
Kathy Hall from the National University of Ireland and Kamil Ozerk from the University of Oslo said in their report: "No other country appears to be so preoccupied with national standards - a preoccupation which is manifested not only in the aims and curriculum rationale but also in the structure of the curriculum and in the nature of the assessment system.
"It seems that England leads the emphasis on published league tables where individual schools are listed in relation to the aggregated attainments of their pupils, thus holding schools to account in a very public way."
They found an education system with more external testing, which occurs more frequently, at a younger age and in more subjects than other countries.
Another report looks at the age at which children start school in England - this is usually four, because of the growing practice of admitting children to school at the beginning of the year in which they become five.
The authors - Anna Riggall and Caroline Sharp, from the National Foundation for Educational Research, question whether four is too young.
HAVE YOUR SAY
It's not about improving the standard of education or the quality of parental choice, it's about providing statistics
Andrew, Wakefield, UK
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."
The authors note: "There has been a continuing concern about the quality and appropriateness of provision for four-year-olds in reception classes. It has been suggested that starting school at such a young age may be stressful for children."
Recent research shows that the youngest summer-born children - those born in June, July and August - perform less well all the way through their education, and gain fewer good GCSEs.
Children in some Scandinavian countries, including Denmark and Finland, start school at the beginning of the year in which they become seven.
Teachers say the findings show the shortcomings of a system driven by testing and league tables.
National Union of Teachers general secretary Steve Sinnott said: "Uniquely, England is a country where testing is used to police schools and control what is taught.
"I call on the government to initiate a full and independent review of the impact of the current testing system on schools and on children's learning and to be prepared to dismantle a system which is long past its sell-by date."
The government has defended its policies.
A Department for Children, Schools and Families (DCSF) spokesman said: "We make no apology for our focus on school standards.
"We want every child to achieve to the best of their abilities, succeed and be happy, and we know that parents and teachers want that too.
"The idea that children are over tested is not a view that the government accepts. The reality is that children spend a very small percentage of their time in school being tested.
"Seeing that children leave school up to the right standard in the basics is the highest priority of government. "
The spokesman said: "Our research finds that while there are no clear links between starting age and attainment, age within year can affect attainment, with 'summer born' pupils doing less well in their early years of education.
"Jim Rose is leading a root-and-branch review of the primary level curriculum to ease the transition from early years into school, to create an even sharper focus on maths and English and to give teachers more flexibility in the school day.
"We have also asked him to make recommendations to improve outcomes for summer-born children and consider whether it would be appropriate to allow greater flexibility in school start dates."
Other key findings from the reports include:-
England has the largest primary schools - with 224 pupils on average.
Educational alternatives, including Steiner-Waldorf schools and home schooling, produce better academic success.
England's curriculum emphasises pluralism, diversity, tolerance and multi-culturalism.
In England, an equal emphasis is placed on English, maths and science, unlike all the other countries, where language is pre-eminent.
The Primary Review is an independent inquiry which is looking at 10 major themes before publishing final recommendations in October 2008.