Passage 2 (2018浙江11月,B)词数:260 This month millions of American kids can forget about classroom bells and set off for grandparents' homes, sleep-away camps and lifeguard stands. But summer vacation hasn't always been a birthright of U.S. schoolchildren. Before the Civil War, schools operated on one of two calendars(日历), neither of which included a summer vacation. Rural(农村的)schooling was divided into summer and winter terms, leaving kids free to help with the farm work in the spring planting and fall harvest seasons. Urban students, meanwhile, regularly had as many as 48 weeks of study a year, with one break per quarter. In the 1840s, however, educational reformers like Horace Mann moved to combine the two calen-dars out of concern that rural schooling was not enough and that overusing of young minds could lead to nervous disorders. Summer appeared as the obvious time for a break:it offered a rest for teachers, fit in the farming calendar and reduced doctors' concern that packing students into hot classrooms would promote the spread of disease. But people's opinion about the modern U.S. school year, which averages 180 days, is still divided.