Well my children exactly fit the findings. DS July born, behind in most things, DD November born, ahead in almost everything.
To be honest I am not happy with the comments here such as:
"As a parent you can counter what goes on in the education system with what you do at home, and your belief in your child."
and
"In my opinion, how well your child gets on at school is far more likely to be driven by the influences and support they get from home, rather than when their birthday happens to be."
Comments like these are negating the influences that are made outside the home, and that there are differences in character that will affect how well children will do. My children have had huge support at home, but the education system is failing my son despite all my effort. Part of this has to do with maturity and how he is treated by the teachers.
Statistics do suggest that lower educated parents vs higher educated parents generally affect the likelihood of a child reaching higher education. But when you have children from the same parents/home, some will do better than others for various reasons, and the way that confidence is built within the education system in the early years can and does, affect childrens subsequent educational journey DESPITE parents support at home.
In Ireland the Drumcondra tests given annually to primary school children, have both class-based and age-based data attached. This allows for the age of the child and birthdate to be taken in as part of the assessment. All children start in September of the academic year, but the age at which a child starts is more flexible.
This flexible entrance year, unfortunately means that you can have a gap of about 2 years in the range of youngest to oldest in a class. Parents often send their children to school as soon as possible to save on child-care costs. The biggest affect is on when the children take the leaving cert (A-Level) exams, where many are ill-equiped to deal with the emotional stress of the exams due to immaturity. Many parents deal with this by making their child repeat a primary school year before moving to secondary school, this has its own emotional price.
OP - if your child is thriving now in school, there is a fairly good chance that this will continue, so I think you can safely put your dd in the 'outside the norm' category, like so many folk have described here, and trust that she will continue to do so well.