When I was in school back in IL it seemed every year right before school started the teachers would go on strike. They usually had it resolved the day before we went back, but a few times it lasted a week or two. In that case, they just added the missed days to the end of the school year, or squeezed them in during teacher work days. Throw in some snow days as well and sometimes we went longer. However, I think they actually built in more days in anticipation of snow, storms, etc as I recall getting out about the same time at the end of the year (I think they were able to "miss" a few days???
alison