My son started testing (both reading and math) in the 99th percentile. Each year his percentile has declined. Reading has stayed relatively strong at 96%, however, math has dropped into the 84th %. He complained all school year of the math being too easy. Seeing his last math scores was concerning as it seemed to indicate he did not learn much math last year - is this correct? I am at a point where I believe supplementing the school math curriculum is necessary in order to keep him engaged and to hopefully bolster his MAPS scores back to the level where they should be. I would appreciate any input on this as well as home schooling program recommendations. Very frustrated! Thank you in advance!

You didn't indicate age or grade level, which would be helpful to understand what's going on here. However, if he's not learning anything new all year, and other kids are, then it would make sense for his percentile ranking to drop, as more kids catch up to his level (at least on the material they're testing on).

Sorry, he's 10, a rising 4th grader.

So in this case, he would not have been learning anything (or at least, anything much) in the last 3 years. Makes sense to me.