This will backfire in my view.
As a child grows in understanding through their teens, the importance and significance is instilled in them, for them to reach out for baptism as a goal.
For a 9 year old to be baptised, they will grow up knowing that decision was actually taken for them, without their realisation of what it entailed or their proper consent.
Baptism will lose it's importance and there will be more who come to resent being forced into something so early in life.