You're not trying to prove that he would benefit from K. That's known. But not terribly relevant from the school's point of view - after all there is something "more" they could do for each individual child to provide a more perfect educational experience, right? Schools can't be a perfect fit for every child and they know this. Think more about proving that 4K would hurt him or that he would be a problem for the 4K teacher. That K would be more cost effective for the school - don't necessarily say that, but they'll be doing the math of 4K with XYZ services versus a grade skip into K.
Expect extreme reservation from the school. Children from enriched home environments are academically advanced in 4K/K but don't stay ahead of peers. By 2nd or 3rd grade they regress to the mean. That's why many (most?) gifted programs don't start until 2nd, 3rd, or 4th grades - to filter out children who would be determined to be gifted by early testing but do not require significant changes to curriculum. The districts save money and conflict by delaying gifted programs a few years. It's an evidence-based decision.
Prepare an argument "he is not likely to regress to the mean because of XYZ data." You'll be looking at performance testing and IQ testing. The performance testing is like looking at what he has learned in the past, while the IQ testing is more like his potential for what he is capable of learning. The IQ test will need to be sufficiently high to demonstrate that he's not ahead only because of home enrichment.
You may want to ask about the outcomes of other students. If your son is 1 standard deviation ahead, ask how other students with similar scores have fared by 5th grade (or the highest grade in the school building). If you're in a data-heavy district, this argument is very strong! When my son was up for a radical grade skip, they compared his standardized test score to the GT students in district. His scores compared to gifted students in 7th grade so he got skipped to 7th grade. If the district has data to show that other students in the district that are scoring similar on IQ test end up needing a grade skip later, then you have more reason to push for it now when social groupings are more fluid.
Don't be afraid to ask how many students are identified gifted, what percent are receiving XYZ services (subject acceleration, pullouts, cluster grouping, whatever), and how many students have been grades skipped in the district.
Thank you for your detailed response. What you said is extremely helpful in making me understand the situation from the school's point of view.
I really appreciate all the helpful advice provided by everyone. I think understanding that this meeting will be for us to finally hear the test results, and just take time to process them was a helpful point.
