Compasses, GPS systems, and maps are useful tools when it comes to navigation—unless you are trying to navigate your way through the results of achievement tests! But with a little bit of explanation, you should be able to understand the types of scores that you'll see on achievement test results and understand how to apply them.

The most frequently used score and most specific score is the National Percentile Rank, or NPR. This is like a scoreboard from a race--it shows how your student's score ranks against the national comparison group for a particular grade.

For example, a score of 73 means that your student scored as well as or better than 73 percent of the students in the comparison norm group.

This is a very different score than 73 percent correct. It is important to remember that percentile ranks are just that--a ranking system.

Sometimes the percentiles will also be shown as a band. There is still a specific percentile rank that the student earned, but the band indicates that the student's actual level may be slightly higher or lower than that actual mark.

A student's scores may vary from day to day, based on how he felt, whether he had good or bad guesses, or whether there were distractions during testing . . . standardized test results take "bad test days" into consideration. The band shows the margin of error. The student's actual achievement level would fall somewhere within that band, no matter which day he tested.