Throughout the history of the United States educational system, much of the control over curriculum has resided in the hands of local school districts. That changed radically with the passing of the No Child Left Behind (NCLB) Act in 2002. This act forced states to take a more active role in the way that their schools developed and implemented content and curriculum. Still, there is a great deal of flexibility that still resides in at the local level. In most cases, schools need simply to follow guidelines developed at the state level.
Throughout the country, most schools follow the same basic curriculum, with allowances for differences in demographics and needs of the student population.
Math: Most states require a minimum of two years of mathematics. This may include algebra, pre-calculus, geometry and statistics. Some areas also offer calculus.
Science: Most states require a minimum of two years of science classes. This may include physics, chemistry and biology.
English: Most states require four years of English. Typical classes include oral languages, compositions, humanities and literature.
Social Sciences: Most states require three years of social sciences including a variety of history course, economics and government.]
Physical Education: Most states require at least one year of gym.
Health: Many states have a health course requirement. Human sexuality, nutrition, anatomy or drug awareness are examples of health courses offered by some states.
The above requirements apply primarily to students on course for graduation. Some states or school districts may offer different choices to a certain degree, but the above-mentioned classes are pretty standard across the country.
It is important to note that in spite of the flexibility offered by the federal government, most states have opted to follow very similar curriculum. This works in favor of students who move mid way through their school careers. This may change as the governement looks at a variety of reform measures.

