If tenured, the salaries are based on the year and back when I did payroll for a school system in Vermont the yearly pay equaled or came close to what others were making working for 12 months. Technically they were not getting paid during the time they were off in the summer, but basically paid the equivalent for the year. The theory was that to remain current they encouraged teachers to take courses in the summer and occasionally get paid extra for things going on in the school. I forget what they called that now. The rest of the staff, teachers aides, were not paid during time off, they were all paid hourly.
Now, please don't mistake what I just said as being critical of that procedure. If it weren't for that we would probably have no teachers at all due to the inability of the public to see past this moment and properly compensate teachers for putting up with their snot nosed demons all day while they sat at home eating bon - bons or something. The wage of teachers is not paying for what their value is. But, I still think it would have been nice to have most of the summer off when I was working. Here in NC there was a movement on a few years ago to have school year round. Most of the schools built within the last 20+ years all have AC. I have no grandkids in the loop at the moment so I don't really know where things are now. I do know that there are some operating year round now. Of course, they were afforded other school breaks during the year that added up to about the same number of school days. As far as I remember, there are about 9 or 10 in North Carolina. They aren't really completely year round, there is a five week break in the summer to stop and take a breath, take a vacation or extensive mental health therapy. We amazingly probably have more snow days then up north because a half inch of snow stops absolutely everything for up to a week or more, if it stays below freezing.