Against when I probably should be for. The actual days in school don't change with year round school for the students. It is just broken up into smaller vacations. For people who live where there are snowy cold winters having a child home for an extended period during this time leaves the child very little to do. Since there are three who are in grade school living here it is not really something I would like. It really wasn't much different in the Sacramento California area where they had year round school either. The cold damp foggy days kept the children indoors anyway.
The original reason for seasonal school was so the older children could help out on the farms that most of the parents ran. This of course for most of the United States no longer applies. If the few areas which it does including the Amish who are wide spread now still need their children home during the summer.
They say from the students standpoint the teachers don't have to spend as much time going over material covered the year before. With the no one left behind rule in effect now this really doesn't make a difference in any school district I am aware of.
From a teachers aspect, there is too much I don't know. Almost every time I have been involved with teaching it was year round. No month long breaks involved. For the most part I taught from people from twelve to thirty who were year round residents at the facilities I was employed by.
From a community standpoint I have lived in areas which had both year round and traditional schooling. The only difference I noticed was less traffic in the winter and more in the summer. I noticed no difference in the economy of areas using either. This doesn't mean there wasn't one, it was just not something that affected me personally.