WIAT vs. WJ for monitoring achievement?


New Member

In the midst of finalizing my son's 504 (which is looking very much like an IEP). We insisted that he be given achievement tests to track whether the interventions he is getting are keeping him at his age/grade performance level.

In his neuropsychologist testing last May, he was given WJIII. The school psychologist (who has been on leave, not sure she has looked at the testing) is proposing that he be given WIAT II. I would think it better to stick with the same test, even though I recognize that he would be given a percentile ranking.

Would one generally expect that there would at least be no drop in the percentile rankings if he is continues to learn what he is supposed to learn in 4th grade (generally he was around the 50th percentile in broad rankings?)

Any views?




Dear Chris,

The WJ III is a psychometrically outstanding test AND it taps a few things that no other test taps. However, because the WIAT II is normed on the same sample as the WISC IV, the percentile ranks are directly comparable. For this reason (and massive marketing) the WIAT is gaining in popularity.

Your are correct: for a child to be learning at the "expected rate," he must not drop in percentile rank. To "catch up" a child must be learning more (and faster) than is typical. If this is true, it will be reflected in rising percentile ranks.

Remember that any test is a reflection of one day and as a result, long term planning should not be based on any single test but rather, aggregated testing over time. In addition to a standardized test at least twice a year, difficult child should be directly assessed on curricular probes to see what he knows in comparison to both what is taught and same school peers (your school should have school-wide CBA data as a BEST PRACTICE--don't be surprised if they do not have it.) Some of my first year students develop school wide CBA norms and are always surprised how some schools are above the national norms and others a below.

Here is an example of how I used the above when engaged in a long-term percentile rank monitoring process for easy child:

At 17 months she was below the 1st percentile in expressive language. By three (after intensive therapy,) she was at the 5th to 8th percentile with all instruments given every three months averaged. By four she was at the 16th percentile and hung out in that neighborhood for a LONG time. Of course she was improving and learning or she would not have HELD percentile rank--but to get her out of the "problem" category and in to average (above the 25th percentile) was tough. It was also a stretch that the 25th was OK because all her other scores were well above the 90th percentile so even 25th would be a relative weakness.

At 6.5, all averaged expressive assessments were right at the 25th percentile. Therefore, direct S/L services were discontinued and she was monitored yearly at Northwestern S/L clinic to MAKE SURE she at least held at that percentile rank. Had she not, therapy would have been reinstituted. She gained very slowly until she was about 12 and landed in the 40th percentile with the residual disability that she cannot auditorally learn a foreign language--which was addressed by her taking Latin in both H.S. and college. I could have gotten her accommodation, but she didn't want it. Latin is not spoken, so it is not a problem for her.

The above reasoning is exactly how Pete Wright won the Carter case before the Supreme court. Percentile rank monitoring is very powerful if it is done consistently and correctly. If there is slippage, there needs to be a change.

So in direct response to your question: I would use multiple measures on multiple days and average the results to monitor percentile ranks very carefully.



Too many parents don't know to ask for this type monitoring. Good catch!


Public school IEPs often fail to include clear base-line data
that provide present levels of educational performance and
expected future levels of educational performance, with
objective measures using grade equivalent, percentile rank and
standard scores. Many parents do not understand that half a
year's progress over a year of special education for a child of
average to above average intellectual ability means that this
child's percentile rank and standard scores will be dropping as
the student falls further and further behind the peer group.