Thank you, aeh. I understand what you are saying, but I still have two main questions.
1)Is the data good enough to be better than no data? Are most professionals in this area pretty confident of that? Can we say the extended norms are valid and reliable?

2)If we differentiate between 160 and 175 and 190, what is the utility of this and what do those numbers mean for a child in terms of an educational pathway (this may be a question best answered with specific data for a specific individual, but just in general)?

Thanks!