在弗吉尼亚理工大学的土木工程师马克·爱德华兹说，大多数学区因为铅治理的费用而不检测他们的饮用水。
Most school districts do not test their water because of the costs associated with lead remediation, said Marc Edwards, a civil engineer at Virginia Tech.
全国超过15000个学区出现了不同的科学和数学教学方法。
Throughout the nation's more than 15,000 school districts, widely differing approaches to teaching science and math have emerged.
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