The Iowa Department of Education considers a child to be proficient if they achieve a national percentile rank score of 41 to 99 on the ITBS or ITED. [See updated information on the Proficiency page.]
The University of Iowa provides a great deal of information about the ITBS and the ITED. Of interest, for evaluating proficiency measures, is how national percentile rank scores are determined and what they tell us about student performance.
A student’s percentile rank is a score that tells the percent of students in a particular group that got lower raw scores on a test than the student did. It shows the student’s relative position or rank in a group of students who are in the same grade and who were tested at the same time of year (fall, midyear, or spring) as the student. Thus, for example, if Toni earned a percentile rank of 72 on the Language test, it means that she scored higher than 72 percent of the students in the group with which she is being compared. Of course, it also means that 28 percent of the group scored higher than Toni. Percentile ranks range from 1 to 99. . . . . A student’s percentile rank can vary depending on which group is used to determine the ranking.
A percentile rank does not tell us how many questions the student answered correctly.
A norm-referenced interpretation involves comparing a student’s score with the scores other students obtained on the same test. How much a student knows is determined by the student’s standing or rank within the reference group. High standing is interpreted to mean the student knows a lot or is highly skilled, and low standing means the opposite. Obviously, the overall competence of the norm group affects the interpretation significantly. Ranking high in an unskilled group may represent lower absolute achievement than ranking low in an exceptional high performing group. (emphasis added)
Without seeing the test questions and the percent-correct answers required to achieve a national percentile rank of 41 or higher, it is difficult to assess how high a bar the Iowa Department of Education has actually set for “good enough” student performance. Another question is whether a criterion-referenced standard of proficiency would provide a better picture of student performance for accountability purposes.