I believe all scores were the grade 2-5 version of MAP. His reading MAP scores are good but not near the upper extreme. Low to mid 90s percentile nationally, mid 80s to 90 percentile locally (we're a high performing district).

His VCI on the WISC-V is in the 99%, his vocabulary is excellent - PPVT above 99%, he has a speech fluency disorder but I don't see how that would impact the MAP scores.

Any reason why scores would stagnate besides lack of challenge?

Personally, I haven't noticed any growth in reading in over a year but have thought that is because once they are "reading", growth becomes less obvious (compared to math).