DS5 is in K, which is relatively academically "advanced" for our area.

He can add and subtract three-digit numbers (and probably beyond). He understands the concept of multiplication, but he doesn’t have the multiplication table memorized.

He has asked me multiple times why the school math homework is so easy. His math homework is mostly number printing, pick out the largest/smallest number from a bunch of numbers, etc.

How important is it to mention to his teacher his ability?