Welcome!
There are many reasons children may test differently on different tests and occasions. Among them:
1. The KBIT-2 is a screener, not a comprehensive assessment like the KABC-2. Similarly, the RIAS-2, though billed as a comprehensive, really isn't.
2. Young children vary widely in their attention, stamina, and familiarity with the testing situation. In addition to local conditions, their rapport with examiners also has a more significant effect on performance than on that of older children.
3. They also experience growth spurts (cognitively, in addition to physically), which may or may not line up with the moment in time at which testing occurs.
In sum, the comprehensive KABC-2 is more likely to be an accurate measure than either of the brief assessments, though the other two do provide some data to keep in mind.
