How to Read ERB's

To read previous scores for St. Nicholas School, see this page for downloads: 
Standardized Test Scores and Summary

Students at St. Nicholas begin taking standardized tests in Level 5 (third grade). This continues in Levels 6 and 7. In the fall the students take the Stanford Achievement Test and in the spring they take the Comprehensive Testing Program 4 (CTP4) produced by the Educational Records Bureau (ERB).

The CTP4 is not one test, but a battery, a series of multiple-choice tests administered to groups of students over the course of several days. The test measures actual performance in areas such as reading, math, and writing skills. It also measures predicted performance in the verbal and quantitative areas. It differs from report cards or evaluations because it is a glimpse of a student’s performance on a particular day. Report cards and teacher comments, on the other hand, represent the average of a student’s performance over a longer period of time.

Median Percentile Graphs:
offer information on how we perform as a school. Included is the 5th grade report for each of the past three years, showing how students in that particular grade performed against the following three norm groups:

All student scores are distributed and redistributed into the following three norm groups:

  • National Norm Group: This group represents all the students  grade level in all schools in the nation. The statistics for this group are estimates based on data from a scientifically selected sample of schools that administered the CTP4 in the process of developing the test.
  • Suburban Norm Group This group consists of students in suburban public schools that use the CTP tests. Students are compared against all of the students in this group who took the tests over the last three years.  This population is more competitive than the national norm group. The students are redistributed under a new bell curve.  Subsequently, a student at the 78% under National Norms may now be at the 47% in this newer, smaller, more competitive group.
  • Independent Norm Group: This group consists of students in independent schools that use the CTP tests and took the test over the last three years. This population is the most competitive because it includes only students in independent schools.  These students have already met and passed rigorous admission requirements in order to gain entrance to their schools.  Students are again redistributed under the bell curve.  Thus, the same student at the 47% under Suburban Norms may now be at the 39% under Independent Norms. 

The median score is the exact middle score. If a grade level has 17 students, their scores would be placed in numerical order and the median score would be the one in the exact middle. Fifteen scores would be on either side of the median score.

Therefore, for each of grade levels, half of our students scored above the line and half scored below it. The median does not indicate the range.
For example, the following scores:
98, 45, 77, 80, 56, 27, 99, 90, 83, 17, 55, 73, 37, 68, 83, 74, 59
Arranged in numerical order:
17, 27, 37, 45, 55, 56, 59, 68, (73), 74, 77, 80, 83, 83, 90, 98, 99
Makes 73 the median score.  

  • The Verbal Ability and Quantitative Abilitysections are intended to be indicators of innate ability as opposed to measures of achievement. Some groups as a whole are stronger than others, depending on the individual students. Because of this, it is difficult to compare different groups of students. 

The bright green bar in each of the test categories represents the median score of the students at St. Nicholas. As a school, we look to see how our median scores compare to the median scores of the Independent Norm Group. We want to be at or above this comparison group or near it if we're below.

Each class may perform differently due to the individuals in the group, creating a little variance over time. Historically, however, students at St. Nicholas perform well in each of the subtests in comparison to the Independent norm group.

St. Nicholas does not test for IQ either in admissions or as part of its standardized testing program. By far, the majority of independent schools use performance on a standardized test as only one of many data points in the admissions or education process. Of greater importance is the average of a student’s performance over time – day after day, week after week, month after month, which gives a more complete picture of a student’s work ethic, preparation, understanding, and attitude.
St. Nicholas chose the CTP4 as one of its standardized tests because it reflects independent school curriculum and is used by the finest independent schools across the country. The items test higher level thinking skills and problem solving, not rote memory skills. It is challenging in many ways!



St Nicholas School 7525 Min Tom Drive - Chattanooga, Tennessee 37421
ph: (423).899.1999 - fax: (423).899.0109 -
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