In my understanding, the CogAT is an ability test which in my mind would mean the scores should be somewhat stable. My DD11 was tested at age 8, again last spring at age 10 and recently at age 11. For example her Quantitative percentile score jumped from 65%/71% (age/grade percentile rank) to 99%/99% (age/percentile rank). Why would there be such a large change?