But it's not you but your child that has to live with it. And it's not just at school but throughout their working lives.
If, by the time they're an adult, a child is sufficiently sick of being referred to by their first name plus surname initial, they will have found a nickname/shortened version to use, or use a middle name, or even change their name!
I once worked in a school with two children with the same name, but it was a unisex name, so one was a boy and one was a girl. The children actively referred to them as 'XXX the girl' and 'XXX the boy', and it never bothered them. Their immediate friendship groups never did this, because they knew who they were talking about (and to staff they were XXX-A and XXX-B).
I just don't think you can choose a child's name based on their school years, that's all.