GED 

GED stands for General Educational Development, and was originally used as the acronym for the series of tests students take in order to earn a high school equivalency credential. Since 2011, both pieces, the tests and the credential, have been referred to as GED.

The test series consists of four exams, one each on math, language arts, science, and social studies. These test your high school academic knowledge, and passing all four earns you the GED credential. This credential serves as your diploma and shows that you have obtained a high school level of education.

GEDs are accepted by employers in place of a diploma.  They are also accepted by 98% of higher educational institutes in the United States. 

The test can be scheduled anytime through the GED website.