The state of Georgia says you must be at least 16 years old to take the GED exam. If you are between 16 and 18, you must show "special needs approval" in order to take the test. People of this age are usually in school, so the state wants to know why you are taking the test before you are of age to graduate.
The idea of taking the GED is to show your high-school level proficiency in five major areas of academics. This is often done to get the equivalent of a high school diploma. Thus, you must not have graduated already from an accredited high school.
You may not be currently enrolled in a Georgia high school at the time you apply to take the GED. The GED is intended to prove that the test taker possesses an education equivalent to a high school education; thus, it is not necessary to continue attending high school.
Official photo identification is required on the day of the test to ensure that the person who signed up for the test is the same person that is taking it.