When should I use Age or Grade Based scoring?

Frequently Asked Question:

When should I use Age or Grade Based scoring?

Answer:

The examiner must decide which score is appropriate for his/her purposes. If the purpose is to determine Ability-Achievement Discrepancy, age-based scores are recommended as "best practice." If the purpose is to compare the student's scores with those of peers in the same grade, grade-based scores should be used. We do not recommend one score over another. We provide both sets of scores because some school districts prefer one over the other. It is best practice to discuss decision-making with the examiner's supervisor or school district diagnostic personnel, as districts have their own criteria for what types of scores are appropriate to report.

Also:

This is a common occurrence, as a single age spans 2 grade levels. For example the 8-year-old sample includes children from both 2nd and 3rd grades. In addition, grade norms include children of the same instruction level, but of differing ages. This discrepancy is present in the original WIAT partly because of increased variance in performance that can allow the discrepancy to be larger (particularly with younger children/earlier grades).