Recently my son (10 years) was tested on both the Woodcock Johnson and WIAT achievement tests. The math scores from test to test were significantly different.

My question is:

What are the possible explanations for the differences in the two test results? How often do differences like this occur?

WIAT III

Numerical Operations 105
Math Problem Solving 123
Math Fluency Addition 114
Math Fluency Subtraction 117

Mathematics 115
Math Fluency 113


Woodcock Johnson III (5 weeks later)

Calculation 130
Math Fluency 121
Applied Problems 127

Broad Math 131
Math Calculation Skills 130


Thank you all