It sounds like he'd be fine acadmemically in kindergarten. I wouldn't be so worried that the school admin will be out to get him, since from her perspective he nearly meets the cutoff, but there's simply a possibility that he won't behave properly since he's on the young side; she's being reasonable by offering the trial period. I would do my best to prepare him to fit into the classroom routine. Impress upon him that he must behave or he'll be out, and back to boring preschool. Find opportunities for him to be in classroom settings before then, if possible, perhaps with local classes of some sort.
