This was our concern too with DD1 as DH had similar issues at school, not challenged, but I've not once heard a parent say the regret sending a child older, only those who wished they'd started them later.

The resources are also limited when it comes to kids who struggle, I've got friends who's kids are struggling with reading, there is only do much more the school can offer/do.

ETA the other thing you will need to consider hot is that if your DD does another year of 4 yr old, it won't be funded, you'll have to pay the full fees out of pocket
I also have heard similar regrets, from parents and the (grown) child too. if only i had a crystal ball.

The kinder field officer said that funding depends on the recommendation of the kinder staff. Funding can be available for a second year under certain circumstances.