My daughter's first day was today as well. Anyone enterring middle or high school had to go in yesterday for orientation. I was actually pleased the princess went to bed early last night and was not a bear this morning.
Here in NY, we always started school on either the Wednesday or Thursday after Labor Day. But we don't end until around the 20th-24th of June, depending on exams and Regents. One winter we had used up all of our "snow days" and the school district had to actually add on extra days at the end of the year. My kids didn't get out until June 30th!
I wish our classrooms had air conditioning. We do get a few really hot, humid days towards the end of the school year and it is not uncommon to have a few in September. Of course, the offices have A/C, but not the classrooms.