“Testing, Testing, One…Two…Three!”
With the new school year off and running, we’re all “back to the grind” in our mission to make a difference for students and the school staff and families who support them. While the majority of students at school make progress with the traditional approaches presented, and/or the various supportive interventions offered through the Response to Intervention (RTI) framework, those with long-term struggles might warrant the detective work that skilled and seasoned diagnosticians can bring to the table with comprehensive testing. The goal being gaining a clearer understanding of the student’s profile of cognitive, neuropsychological and academic strengths and deficits, allowing us to develop meaningful educational interventions that school staff and parents can use to support student growth and success.
“What do all those numbers mean?”
As skilled, seasoned and committed clinicians, we not only have a responsibility to get an accurate read on a student’s cognitive profile, but most importantly, to be able to communicate what those scores mean for that student’s day to day classroom performance and prognosis, as they move forward.
But all those scores and numbers can be totally daunting, and even frustrating for parents, teachers and other school staff bombarded by them. When looking at the columns of test scores, it’s easy to get overwhelmed!! You’ve got Raw Scores, Standard Scores, Percentiles, T scores, Z scores, RPI scores, W scores and so on.
The Normal Curve and the Standard Score
Most diagnosticians try and help others make sense of test scores by plotting a student’s Standard Score on the Normal Curve, which looks like the picture below.
The Standard Score tells us where the student’s performance falls on a particular test measuring that ability, in comparison to other students their age in the normative sample of students taking that test. The Mean is the “Average” score, and Standard Deviation (SD), how far above or below the Mean a student’s particular score falls. All scores between -1 and +1 SD are considered to be within the lower and upper ends of Average. As the curve flattens at each extreme (2-3 SD above or below the mean), only a very small number of students achieve scores at those very low and very high levels.
By plotting a student’s profile of Standard Scores on various test measures, we can see how they perform in comparison to others their age. We are also able to compare their profile of skills relative to one another, providing a picture of their unique pattern of strengths and weaknesses.
"When is the Standard Score NOT the metric of choice?” "Why is my child/student STRUGGLING academically when his or her Standard Scores fall within the “Average Range?”
In our over 30 years as School Psychologists, there were many times we couldn’t explain why students with Average Standard Scores were still described as struggling by their teachers and parents, and even found ineligible for specialized services they truly seemed to require.
As School Psychologists, our responsibility to communicate the meaning of scores, both verbally and in our reports, may have fallen short when we relied solely on norm referenced Standard Scores to tell the whole picture. Those scores served an important role, but seemed inadequate when needing to describe the nuances of day-to-day academic performance.
While appropriate to describe cognitive sub-skills (e.g. memory, attention, visual perception, reasoning, etc), Standard Scores may be insufficient measures in some cases. While Standard Scores and Percentile Ranks describe a student’s relative standing, or rank order, compared to age or grade peers, they are not sensitive to the quality of their performance. They are not sensitive to identifying the nuances of specific learning skills and/or styles of a student’s performance, which impact their daily performance in school, and their overall acquisition of academic skills.
We now know that more refined measures may be required to identify the nuances of daily and incremental growth in academic learning.
Here comes the Relative Proficiency Index (RPI)
RPI is a statistical measure that DOESN’T tie into the Standard Scores or Standard Deviations, and is not generally found on most tests out there.
The Woodcock Johnson Cognitive and Achievement tests allow for this unique and meaningful measure of progress and proficiency on tasks that Average peers can perform. The RPI displays how PROFICIENT or FUNCTIONAL a student is on specific tasks compared to Average peers their age or in their grade. It indicates the range of development or level of instruction a student can tackle (independent, instructional, and frustration levels) and, how EASY or DIFFICULT a task at that level will be for the student.
Although a bit complicated to understand, the RPI is represented as a fraction. The denominator remains at 90, and the numerator ranges from 0-100. Scores range from 0/90 to 100/90. The student’s expected level of success is the numerator, and the 90% criterion is the denominator. For example, an RPI of 60/90 suggests that the student would be about 60% successful on a task that typical peers would perform with 90% success.
A proficient score (e.g. 96/90) would suggest that tasks at that level would be EASY for the student to perform. A non-proficient score (e.g. 48/90) would suggest the student likely struggles when tackling tasks at the level most other peers of that age or grade could manage 90% of the time.
A closer look at these Relative Proficiency Index (RPI) scores is really necessary to better understand qualitatively why a child with Standard Scores in the Average range, might be failing to master academics at an Average level. It is a more sensitive measure with implications for classroom performance and really supports what teachers and parents report! This has strong implications on many levels, including their importance for consideration at CSE eligibility meetings!
Stay tuned for further discussions on the W Score as another important statistic.
Tina K. Goldman and Roni Kramer