Education standards must apply to all states and districts. Standards will keep states and districts from falling behind. No child from one state or district should be privilege to a "better" education than any child from other states or districts.
Developing a national standard for public education is difficult because different geographical areas have different educational resources avaliable; towns and cities with large universities and a surplus of colleges tend to attract more (and more highly eductated) teachers and educational resources that are more difficult to quantify than tax dollars. It is impossible to give every person access to the same quality of education, even without considering the effect of family, friends, and other social influences on a person's eductaion. Nationally uniform education standards inherently favor people from certain geographical areas and socioeconomic strata.