You don't need to fill it in but I figure they put it there for a reason! If my application is up against another then anything that can sway it my way is good.
I made a few points in the box:
That she goes to the nursery that is on school grounds and is thriving, I believe staying in the environment she knows will be a huge benefit to her and aid her settling into reception. Also that many of her peers at nursery will be going to the school which will help her settle.
That it's the only school she can walk to- something that's important to me and is meant to be a good start to the school day, as well as good for health and the environment.
That we moved to the area for the school as we know it to be a good school and that I went there as a child so it's important to me.
Obviously these points may not be valid for you but if you can think of something I'd put it down, you never know what might help! Is there something about the school that particularly suits your Lo? Maybe it excels in sports or music and your child loves sport/music? Or it's a small school and your LO is quite shy and you think a small school will help him feel more confident?
Anyway, hope that helps. Fingers crossed for April!