It sounds as if you failed to meet the minimum testing standards during initial training. If so, it is unlikely you would be of much benefit to the guard, which uses the same equipment as the Air Force.
Discuss your situation with your ANG recruiter to be sure.
The foregoing is for general information purposes and does not establish an attorney-client relationship.
Every situation is different. Contact a recruiter for assistance. If you aren't sure about the answer you get, give my office a call. I would be happy to assist you in trying to join the Guard. Consult is free. Good luck.
I suggest you get help from your First Sergeant, Area Defense Counsel, and the Military Personnel Flight to find out what your re-enlistment code will be. The personnel code placed on your record, based on the basis for discharge, will determine whether any other branches (or the Air Guard) will allow you to re-enlist. But I agree with the other comments that re-enlistment into the Air Guard is unlikely considering the Air Guard is still the Air Force.
Providing this general response does not create an attorney client relationship.