19 Tex. Admin. Code § 89.45
An examinee who fails to achieve a minimum passing score on one or more of the tests may retest on the tests he or she failed, except for instances in which the American Council on Education establishes that scores may not be combined across a General Educational Development test series, in which case the examinee must successfully complete the full battery of tests in a series. Each retest must be on a different form of the test.
Source Note:The provisions of this §89.45 adopted to be effective September 1, 1996, 21 TexReg 5690; amended to be effective April 18, 2002, 27 TexReg 3061; amended to be effective December 11, 2011, 36 TexReg 8373.