Many states/districts have rules about min. age for K-1 but in 2nd grade there is not a limit. Many people around here with kids just days past the cutoff will do private school until 2nd grade (ie start private school early and then just enter public later).
There is also a district policy to allow testing to advance a grade once the kids are entered in school. In elementary it's difficult to achieve mainly because kids have get high scores in all four core subjects and there may not have been exposure to the tested specific concepts in science and social studies.
Just sayin' like others have suggested there may indeed be a procedure or policy, it just may not be publicized. I found ours by hunting around on the district website or googling "XXXISD legal policy" or something. They need to have this in place for transfer students from other districts and out of state.
