I wrote a report at the end of each year that summarized what we did (and at what level) and also listed all the resources we used. I also had my son take a standardized test each year, always out of level. We started a year above age-grade level in K and by the time he was in 4th grade, he was taking the test three years above age-grade level.
When we applied to a private school for 6th grade (which was a one year skip), I submitted these documents with the application. when we asked for an additional skip at the end of 6th grade, there were no problems getting it.
