Children who have access to a qualified teacher at nursery do only slightly better at age five than their classmates, research suggests.
A new study concludes that a youngsters' educational achievement at the end of their reception year is only very slightly higher if they have been taught in a nursery with a teacher trained to graduate level.
There was also little difference between those attending a nursery rated outstanding by Ofsted and others.
Researchers from the Centre for Economic Performance at the London School of Economics, Surrey University and University College London, compared data on children's results with information on nurseries attended in the year before starting school for around 1.8 million youngsters born in England between September 2003 and August 2006.
The findings showed that children who attended a nursery that employed a graduate have a teacher assessment score around a third of a point higher, where the total number of points available was 117.
And attending a nursery judged as outstanding was linked with moving up less than one level more on just one of the 13 scales that make up the early years foundation stage, which assesses what children can do in areas such as literacy and numeracy at age five.
The researchers did estimate whether similar children who attend different nurseries then achieve different results in reception, and found that the results do vary depending on the nursery attended, but not in a way that is predictable by staff qualifications or Ofsted judgments.
Dr Jo Blanden, senior lecturer in Economics at Surrey University, said: "Successive governments have focused on improving staff qualifications, based on the belief that these are important for children's learning. Our research finding that having a member of staff qualified to graduate level working in the nursery has only a tiny effect on children's outcomes surprised us, given existing research that finds well qualified staff have higher quality interactions with children.
"It is possible that our results are partly a consequence of the types of qualifications held by those working in private nurseries, as these are not generally equivalent to the qualifications of teachers in nursery classes in schools.
"Some nurseries are helping children to do better than others, but this is not related to staff qualifications or Ofsted ratings.
"It is extremely important to discover the factors that lead to a high quality nursery experience so we can maximise children's chances to benefit developmentally from attending nursery, particularly as the Government extends the entitlement from 15 to 30 hours."