The Iowa Acceleration Scale is used if they are considering to move your son up to a higher grade in certain subjects or even for a full grade skip. (it was used with my dd for a grade skip) Part of the IAS has questions/rating scales based on how the child performed on above-level testing.
I suspect that the school was giving your ds a "third grade test" as an above level test so that they would have some information about your son in order to complete that section of the IAS.
When they finish all the sections of the IAS, they will add up the points for each item/rating scale and it will be used to determine if your child is recommended for subject or grade acceleration.
