Is it possible that the discontinue rule was hot right at the 19 value? My child has one 19 without extended norms and he also had extended norms for an 18 because discontinue rule was not hit.
The discontinue rule shouldn't matter. You can get a low score without hitting discontinue rule (e.g. DS got two 15s this way; a lot of wrong answers, but not enough consecutive to discontinue.) What matters is if the scaled score is at the ceiling. Then it's possible that extended norms could give a higher score.
