There is no "off" season in my book. A site worth seeing is worth seeing year round. I don't do heat well. I get that clammy and nauseous "I'm gonna faint feeling" pretty quickly if it's above 95 degrees F. So, I'd much rather go on trips during the other three seasons. I think it would make sense for public schools to have their off season spread out during the year because I'm sure there are others like me who would enjoy their vacation trips a lot more if they could walk about without fear of fainting.