A new report suggests that half of children in England are not ready for school by the time they enter Kindergarten.
According to the data, only about 52% of five-year-olds have reached "a good level of development." In some areas, that number is as low as 28%.
The report comes from Sir Michael Marmot, director of Institute of Health Equity at the University College London, who has been keeping track of the health inequalities in England since 2010.
"We continue to fail our children. How can this still be happening? For three years the Institute of Health Equity has published evidence showing we are failing our children. It is unacceptable that only half of our five years olds are achieving a good level of development," Marmot said.
In 2011, the number of young children developmentally ready to enter Kindergarten was 59%. That number has dropped 7% in only 2 years.
"When we first looked at these figures we assumed there must be something wrong with the measurement. How can it be the case in England, one of the richest countries in the world with our long history of being a brainy country, that only 52% of children can have a good level of development?"
Marmot added that in comparison to other European countries, England is "doing really badly."
The data shows that children living in impoverished areas tend to lag behind their peers in developmental and educational milestones set by the Department of Education, such as listening and paying attention, using the toilet and getting dressed, as well as beginning to read, write and perform simple math.
Research has unanimously shown that those children who lag behind in elementary school will continue to do so later on.
"We need real action to improve the lives of families, support good parenting and improve access to good quality affordable early years services. The evidence is clear; we have to get it right at the start if individuals are to achieve the best possible health throughout their life."
Of the children who are part of the free meal program, only 36% reach the target goals for development, leading Marmot to state that the Closing Sure Start children's centres, which began as an effort to help low-income families, are "not a good way to improve early childhood development."
In 2007, the UK was rated in the bottom 21 of developed countries for child wellbeing by UNICEF. The rating was based on things like infant death, teenage pregnancy, and employment. Last year the UK was raised to position 16.
The Department of Education is responding to these concerns by changing the way that children's development is measured, making the current measures of children's development no longer mandatory.
A Department for Education spokesman said: "No child should start school behind their peers. This is why our plan for education is providing flexible, affordable and good quality childcare.
"We are raising the status and quality of the early years workforce by introducing rigorous new qualifications so practitioners are highly skilled and can help all children reach the expected level of development. Furthermore, we are investing £50 million from April next year to extend the pupil premium to the early years."