Yay, you answered the question that strictly speaking was asked but everyone understood what was wanted by the OP. You’re very special. Now are you going to contribute for real or was that it from you?
My school days always started the tuesday after Labor Day and ended in June somewhere. I didn’t really pay that close attention. I liked school and would have liked to have gone year round.
I started Cubertson elementary school in south Georgia. I know we always went to school for one day then out the next school day because it was a holiday… Dropped out of school in 1964, got married, went back in the seventies, then again in the nineties…
Yeah, I can understand the benefits, but it makes me kind of sad to think of the poor little modern tykes never having that “Whee! I get to play for 3 months!” feeling at the end of June. (Also, as an adult without children, I like being able to anticipate a child-free vacation September through May.)
I suppose that if this trend continues, summer camps will disappear like the drive-in theaters of yore :(.
Aaaaaand, once again I shoulda read the entire OP.
Went to school in MA in 80’s and 90’s. Same here.
Usually right after Labor Day to the end of May for me, went to school in MS, TN, CA and back to MS. Two weeks off for Christmas, two for spring break.
My son boards, and we live in Australia. He goes at the end of January, usually the day or two after Australia Day on January 26th, and is out the first week in December. He’s home three times during the year, for two weeks at Easter, three weeks in July and two weeks in October. *
*Or any other time I need/want him to come home, really, since it’s just three hours or so by train, although I don’t like him missing too much school. In practice, he misses one day a month to come home for his appointment with his orthodontist. I also try to get him home on his birthday in August as well.
My birthday is August 19th; I don’t recall ever being in school on my birthday. K-12 was in Springfield, Illinois, in the 1970’s and 80’s. I know school started well before Labor Day, though. So maybe around August 25th, or thereabouts?
When we got out was a crapshoot; snow days were tacked on at the end of the year, there were semi-frequent teacher strikes requiring days tacked on at the end of the year, etc. Usually we were never in school past the first week of June.
In Baltimore county in the 60s and 70s, school started the day after Labor Day and ended the second week of June, usually with half days for the last couple of days.
How long have you been in San Diego? September and early October are usually miserably hot, and May and June are quite cool. Even early July can be cool compared to October.
When I was a kid in San Diego, on the year-round system, we started in July. When we switched to summers off, I think we went early September to June. I have memories of baking in “bungalows,” those portable “temporary” classrooms that did nothing to mitigate the 100-plus-degree heat.
ETA: I know L.A. gets hot too, but I don’t know if it has the same weather patterns.
Started school in 1978.
The hours of the day were:
Kindergarten- 8 am to Noon.
First and second grade- 8 am - 2:30 pm
3rd, 4th and 5th: 8 am - 3 pm.
6th, 7th and 8th: 8:40- 3:40 + sports practice.
9th-12th: 8 am - 3 pm.
Generally speaking, in the earlier part of my scholastic career, we started around Labor Day, but as time went on, we eventually ended up starting about August 20th.
Sophie went to Kindergarten from 8-2, 1st-4th grades were 7:55-2:55. Looking at the schedule, in 5th grade she’ll go from 7:55-3:15.
I’ve been in San Diego for 26 years. The end of August and the first week of September are generally the only uncomfortably hot times. Of course, it varies a bit by year and by area. I remember going to Wild Animal Park over Christmas vacation one year, and it was 35 (~95 F) degrees.
I can’t wrap my head around starting school on any day but Monday. That way you’re looking down the barrel of five days before a respite. Schools that ease you in by starting in the middle of the week are missing an opportunity for devouring your soul, which is of course their primary mission! 
San Diego Unified went back to school on September 6th; Los Angeles Unified is back today (Sept. 7th).
I went to school in Houston and it always started in late August, like say Aug 24th. We got out in late May.
Now I live in Tucson and school here starts more like Aug 11th and is out mid to late May, say May 23rd.
In Maryland suburbs of DC from '63 to '76. September to June every year.