Answer:
To become a classroom teacher the specifics vary from state to state, however, with the new No Child Left Behind laws the basic qualifications are:
You must have a college degree - Bachelor's (4 year) or higher.
You must pass a content mastery test in whatever subject area you wish to teach.
You must pass a Professional Pedagogy test. (A kind of what would you do/why would you do it test.)
Some states require additional training but "Trade schools" are not accepted unless they are part of an accredited degree program.
You do not have to have an "Education" degree i.e. Social Studies Ed., Math Ed., Science Ed... However, if you do not, you will have to go through what is known as an Alternative Certification Program. Requirements for admission to and completion of these programs vary widely depending on the state and the program you wish to enter.