I'll just confirm all said above re:
1. instability of preschool scores
2. relatively low correlation of the KBIT screener to comprehensive tests
3. re-testing with a comprehensive cognitive assessment, like the WISC-IV or -V, if you want to know where he is now.
I would echo polarbear: symptoms interpreted as complacency or inadequate challenge, or any other inconsistency you see between your holistic sense of his ability and his actual academic performance, may be indicative of an impediment to learning, such as an LD. Certainly, before ascribing it to poor motivation or effort, I would want to rule out elements not within his control.
