In my time Labor Day was the unofficial end of summer, because school began after Labor Day.
Today school begins almost a month before. When I was in school that would not have been possible, especially in the South. The schools were not air-conditioned. If school had started in August no one would have showed up. It was difficult enough getting through May before school was out in June.

As most Americans probably thought of Labor Day as the last summer holiday, now that Labor Day has lost that role, what is Labor Day? The holiday originated as an apology capitalists tossed to labor to defuse a standoff.

Workers understood that labor was the backbone of the economy, not Wall Street moguls or bankers in their fine offices. Workers wanted a holiday that recognized labor, thus elevating labor in public policy to a standing with capital. Some states created labor day holidays, but it wasn't until 1894 that Labor Day was made a federal holiday.