[讨论]一道逻辑题，请教~

A report of a government survey concluded that Center City was among the ten cities in the nation with the highest dropout rate from its schools. The survey data were obtained by asking all city residents over the age of 19 whether they were high school graduates and computing the proportion who were not. A city school official objected that the result did not seem accurate according to the schools' figures.

The school official can most properly criticize the reasoning by which the survey report reached its result for failure to do which one of the following?

The answer is:

distinguish between resident who had attended the city's schools and those who had received their schooling elsewhere.

文章的题目我反复读了很多遍，我觉得我是看懂的。就是说，政府的调查是基于询问了所有年龄大于19岁的城市居民是否获得大学学历，然后计算得出那些没有的人的比例。但是一个学校官员反对这个数字，说与学校所掌握的数字不相符合。

问题是：学校官员如何criticize政府报告中所运用reasoning  that the survey report reached its，其实就是变相weaken吧

但是我的疑问是：

如果报告得出这个城市的dropout rate from its schools的比例最高，那么就是调查过程中，回答具有大学学历的人数应该很低，因为报告是取反的。既然如此，政府官员要weaken这个结论，跟是否则这个城市读书还是别的地方或的学历有什么关系? 是不是说其实这个城市所有那些dropout的人中，有一部分是drop out of the school in other cities？

请教~

文中说，the survey data were obtained by asking all city residents over the age of 19，那么就不存在不具有代表性的情况了呢