Lacey: When the school is trying to determine ability/achievement can they use to different tests? For example: Can they use the RIAS 2 to determine ability and then compare it to KTEA 3 for achievement? Or do they have to use the same test to determine “ability/achievement”? If two different tests are used…how do you know the two scores will be credible when compared to one another?
Yes, you can use two “different” tests to document an ability/achievement discrepancy. Tests that are normed and developed together (such as the Woodcock-Johnson Cognitive and Achievement tests) usually have higher correlation/agreement than tests that aren’t developed together–but different tests can be used successfully as long as the correlation is taken into account. For example, the KTEA 3 manual provides correlation tables for the KABC-II and the DAS-II. Because it doesn’t report correlations with the RIAS-2 best practice would be to use the default correlation of .62 to compute ability/achievement discrepancy. The school psychologist should be able to provide you with all of this information for the chosen tests.