Originally Posted by madeinuk
A drop of basically 4 standard deviations (assuming sigma=15) just does not seem plausible without something else going on. This isn't regression to the mean as much a 'reflection' about the mean almost as though someone was reading from the wrong end of the chart. I would follow this up IIWY

I think the OP means that her son scored in the 69th percentile,not a 69 SAS. The SAS for 69th percentile is somewhere between 105-110, which is around 2 SD different from the GAI of 135.