This is an iffy thing. Some schools want you to put any disadvantages you might have had in that extra space. Unless they are severe disadvantages, don't put any down.
Bikini is right about some schools. It would help to put a blurb that specifically states what appeals to you about the school. Some schools might not even care if they see it though. Usually it wouldn't hurt to write that blurb though.
It's case-by-case though. What secondaries?