Because intelligence tests are norm-referenced, a high score does not differ with age. Norm-referenced tests are different from the kinds of tests in which the score is based on the percentage correct. Norm-referenced tests compare an individual's performance with that of others his own age.
The average score on any test is the 50th percentile. This means that half of the population scores at or above that score, and half score at or below that score. On most intelligence tests, the average score is 100. This means that half of the population score 100 or better on an IQ test and half score below 100. According to the Wilderdom website, scores of 85 to 115 on an intelligence test are in the average range, as 70 percent of people will score somewhere in this range.
According to the Wilderdom website, an intelligence score of 115 to 124 would be considered above average. A "gifted" score is a score of 125 to 134. An IQ of 134 to 145 is considered "highly gifted." An intelligence test score above 145 is usually referred to as "genius" level.