Was the grade in question 3 or 4, by any chance? Florida has messaging about FCAT performance in grade 3 in order to promote to 4. Nominally, local school districts may make their own promotion/retention decisions, but districts interpret this different ways. They may have delayed official documentation to get around this FCAT consideration, or to avoid giving him the FCAT a year earlier than anticipated (which makes their school test numbers look worse/not as good). A related possibility has to do with the grade of record as of the official state enrollment count date (often October 1st), which determines both funding and standardized testing grade in many states. If they changed his grade assignment after the count date, it might have interfered (again) with school test data for that school year.
