Arc Guide to Special Education Evaluation Terms

Terms used in special education evaluations can be confusing. Test scores may be reported in a variety of ways including age equivalents, grade equivalents, raw scores, scale scores, subtest scores, and standard scores. These scores often show the age at which most people can do a skill or task. Scores may compare a student’s performance to others of the same age and may show the student’s position on that test relative to a group of similar-aged students. The goal of testing is to obtain a description of the knowledge and/or skill of the student.

This Arc Guide explains commonly used terms.


Average Score/Mean Score

  • Number or score that is obtained by adding up all the numbers and dividing by the amount of numbers. For example, 15 + 5 + 10 = 30, divided by 3, average is 10

Age Equivalent Score (AE)

  • Provides age at which most people can do a skill or task
  • Compares student’s performance to that age
  • Almost always used for tests of intellectual ability (IQ)

For example, if a 5 year old student gets a raw score of 20 on a test, and that is the average score for 5 year olds, the AE would be 5.

Bell Curve

  • An imaginary curve used to show scores on a test
  • This curve is graphically represented as a bell, with equal numbers on each side and approaching zero at the ends
  • Most individual scores would be at the top of the bell with a curve narrowing to the fewest individual scores on either end of the curve

Cluster Score/Composite Score/Index Score

  • An overall score made up of several subtests
  • Important to look subtest scores to identify areas of strength and need

Confidence Interval/Confidence Level

  • Also known as margin of error
  • The range in which a student’s scores will fall within a certain percentage most of the time
  • A measure of how the result/score is probably correct
  • Most confidence intervals are 95% or 99%

Criterion Reference

  • Determines whether or not a student meets a certain skill or content level (something the student does/does not do, and/or how much they do); is not compared to other students
  • Description of what a student should know or do at a specific age

Full Scale Score

  • Usually used for intelligence (IQ) tests
  • Overall score for several tests of verbal understanding, reasoning, memory and speed using spoken and picture prompts

Grade Equivalent Score (GE)

  • Compares the student’s performance on grade-level activities against the average performance of students at that grade levels

For example, a GE of 4.5 in math means the students solves math problems similar to the average 4th grader

  • Scores show an overall approximation of grade level abilities


  • Average level of ability or skill for most people
  • Scores often compared to others of the same age (age normed) or grade (grade normed)

Norm Referenced

  • Compares scores to the average student scores of the same age or grade level
  • Puts students in order in relation to others in a selected group

Percentile Rank

  • Divides everyone’s scores into 100 equal parts
  • Compares the student’s score to the students at a similar age.

For example, if a student obtains a percentile rank of 70, the student performed the same or better than 70% of the other students

Raw Score

  • An original student test score that has not been changed for interpretation or adjusted for position in relation to others’ scores
  • Describes tested number of items answered or done correctly

Scaled Score

  • Change of the raw score to a common scale that can be used for comparison to others’ scores

Standard Deviation (SD)/Standard Score

  • Measures the amount a specific score is from the average/mean score
  • In most educational and psychological tests, the mean/average is 100 and the standard deviation is 15. The mean is zero standard deviations.
  • A number indicating the difference a score is from a group
  • Indicates how widely individuals in a group vary (The more the group varies, the higher the standard deviation)
  • Average scores are between 85 –115

Standardized Test

  • Requires all test-takers to answer the same questions, in the same format, same instructions, same scoring to allow scores to be compared among students

Subscale/Subtest/Subtest Score

  • Short tests within a large test
  • Measures a specific ability/skill that is combined with other subtests
  • Two or more related subtests that test different parts of the same broad ability or skill

T scores

  • Used for social, emotional and behavioral tests such as the Behavior Rating Inventory of Executive Function (BRIEF) and Behavior Assessment System for Children (BASC) and are converted to percentile ranks
  • Have an average score of 50 and a standard deviation of 10
  • The farther away from 50 the score is, the more different it is from a usual score



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