The debate around school starting-age has been reignited by a row over a council's policy on deferred entry to P1.
Edinburgh City Council has rejected a higher proportion of pleas for discretionary deferrals this year - 61 per cent compared with 46 per cent last year.
This has led to claims from parents that it has toughened its stance.
The authority, however, argues that under Curriculum for Excellence, P1 is now more of a continuation of nursery, so there must now be a strong reason to defer entry.
The mother of one child who has just entered P1 at Craiglockhart Primary in Edinburgh described the council's decision to turn down her application for deferral as "unfair and misinformed".
The parent, who did not want to be named, told TESS that her son was not ready in terms of social development or maturity for school. However, despite his birthday falling just seven days short of the council's automatic deferral date, the family's application and appeal had been rejected.
The council had cited changes under Curriculum for Excellence for refusing the deferral, she said.
But it had not taken into consideration the major differences between school and nursery, she felt.
"The length of the day and the fact they have to cope on their own in the playground and go to the toilet on their own - it's very different and a child needs maturity, but they just don't care about that."
The council had said that older children may make better progress in early primary but that this usually evened out by the end of P3, she said.
"If that's the case, you could be talking about three years where your child is significantly less able than everyone else in the class."
Edinburgh City Council's current policy is that if a child's birthday is in January or February and parents apply for deferral, they will automatically be granted an extra year at nursery.
However, if the child's birthday falls between the first day of the autumn term and 31 December, the deferral is "discretionary".
Edinburgh's education leader Marilyne MacLaren said a child's entry to primary should not be deferred "as a matter of course". The only reason for keeping a child for another year in pre-school should be "because all evidence points to developmental delay and that another year in nursery would be beneficial to progress," she said.
"Through Curriculum for Excellence it's much less the case that a child needs to be ready for school and more that schools are now ready to adapt teaching approaches for all children," she said.
But Alan McLean, an educational psychologist and author of The Motivated School, said that the "overwhelming demands" school makes on young children, particularly boys, were not being fully appreciated.
"My research has strongly suggested that in primary schools it is peer dynamics that drain pupils' well-being and motivation," he said. "And it is the immature boys who suffer most from peer adversity because of self- control and emotional regulation issues."
Nationally, deferral requests by parents of four-year-olds have increased substantially over the past decade: in August 2010 3,371 parents deferred entry, compared to 2,165 in 2001.
Number of applications for P1 deferral in Edinburgh
Total applications (automatic and discretionary):
2011-12 - 459
2010-11 - 542
Discretionary applications only:
2011-12 - 107
2010-11 - 175
Discretionary applications approved:
2011-12 - 42
2010-11 - 95
2011-12 - 65
2010-11 - 80
Source: Edinburgh City Council.