Test scores can and do change over time (which is why we retest), but that seems like quite a large jump. My vote is for administration issues in one or both (!) testing sessions. Impossible to guess which one was "right." Newbie testers are sometimes much too easy (they feel bad for the kid and try to coach them or give them the benefit of the doubt) and sometimes much too hard (they forget to query or don't pattern-match well on the judgment-call tests) and sometimes just plain weird (grin).