We can no longer afford an academic calendar designed when America was a nation of farmers who needed their children at home plowing the land at the end of each day. That calendar may have once made sense, but today, it puts us at a competitive disadvantage. Our children spend over a month less in school than children in South Korea. [emphasis added]Our President may know many things, but not farms. (Or, more likely, his speechwriter(s) don' know farms.) Farm kids do plow, did plow. My grandfather remembered breaking a field in southern Illinois probably at the end of the Civil War. But getting out of school early in the afternoon in order to plow isn't and wasn't standard practice. They could have said "...at home to do the chores, milk the cows and feed the chickens." That would fit if they're concerned about the short school day. (Some charter schools, particularly KIPP, make a point of lengthening the school day.
Or, if they're concerned about the short school year, they could have talked about tending the crops, doing the haying, harvesting. That would vary depending on the area and the type of farming.
(On something different, if I read it right Iowa went from 5 percent to 45 percent of corn planted in about a week. I know modern equipment can cover lots of ground very fast, but that seems incredible. Must have been a lot of 16-hour days.)