This seems to be becoming more common with more schools gaining academy status & setting their own admissions. Two of the schools we are likely to be applying to use this system. Within each band they will apply the over-subscription criteria, meaning if your child is placed in band 4 for example, and they come as 31 on the criteria they may not get a place
I think it will be more of a problem if your child is 'average' rather than well below or well above, as these will be the fullest bands. I have a feeling that in reality if your child's band is over-subscribed but there is space in he band above/ below they will be offered a place but I have no concrete evidence for this.
We have been advised to make sure among our 6 preferences is a school fairly close and a school that doesn't use banding to ensure we are offered a place.
But yes, of course we as parents get a choice in our child's school