It's the same list of questions for every kid aged 6-16. It is age normed. For a 16 year old to score a 19 (i.e. +3sd) on a subtest (even with extended norms available) they basically need to get every question right.
[Editted by 22B] As a pure example: A sub-[test] [e.g. similarities] may have [44] progressively harder questions, an eight year old may hit the ceiling after getting [29] correct generating a scaled score of 19 (which is 3 standard deviations above the mean.)
A fourteen year old may get a scaled score of 19 with [42] correct.
