A stanine score is a standardized testing scale from 1-9 that groups student performance into nine categories, with 4-6 considered average. The term combines "standard" and "nine."
What is a Stanine Score?
A stanine (short for "standard nine") is a method of scaling test scores on a nine-point scale with a mean of 5 and a standard deviation of 2. Originally developed by the U.S. Army Air Forces in 1942, stanines have become standard for reporting achievement test results. The system converts any test score into a single digit from 1-9, making results easy to interpret at a glance. Stanines 1-3 indicate below-average performance, 4-6 represent average performance (where most students fall), and 7-9 indicate above-average performance.
Key Takeaways
- Scale runs from 1 (lowest) to 9 (highest), with 5 as the mean
- Stanines 4-6 are considered average and include about 54% of students
- Stanines 1-3 are below average; 7-9 are above average
- Simpler than percentiles but less precise
- Some states use stanine requirements for homeschool compliance (e.g., Virginia requires 4th stanine)
The Stanine Scale Explained
Stanines vs. Percentiles
Percentiles and stanines measure the same thing differently. A percentile shows exactly where a student ranks - the 75th percentile means scoring higher than 75% of students. Percentiles use a 1-99 scale, providing precise information. Stanines group those percentiles into nine broader categories, sacrificing precision for simplicity. A student at the 42nd percentile and one at the 58th percentile both receive stanine 5 - they're both "average" even though one scored noticeably higher. This grouping is actually a feature, not a bug: it prevents over-interpreting small differences that may not be educationally meaningful.
Why Schools Use Stanines
Stanines remain popular despite their limitations for several reasons. A single-digit score is immediately interpretable - parents don't need statistical training to understand that 5 is average and 8 is strong. The broad categories reduce over-reaction to minor score variations; students near a boundary might get different percentile scores on retesting, but usually stay within the same stanine band. For quickly identifying students who may need support (stanines 1-3) or enrichment (7-9), stanines provide efficient classification. They also allow rough comparison across different tests and subjects since all stanines share the same scale.
How Homeschool Parents Should Interpret Stanines
When reviewing your child's stanine scores, remember several key points. View as a snapshot: Scores reflect performance on a single day and may be affected by illness, anxiety, or distractions. Look for patterns: One low stanine isn't cause for alarm - look at trends across tests and subjects over time. Understand the average range: Stanines 4, 5, or 6 mean your child is performing with the majority of same-grade students. Use diagnostically: Stanines can highlight subject areas needing attention or areas of strength worth nurturing. Don't over-interpret boundaries: The difference between stanine 5 and stanine 6 may not be educationally significant - there's considerable overlap within bands.
The Bottom Line
Stanine scores offer a quick, accessible way to understand where your child's performance falls relative to national norms. While less precise than percentiles, they provide enough information for most purposes and prevent over-interpreting small score differences. For homeschool compliance in states like Virginia that specify stanine requirements, knowing your target (typically 4th stanine or above) helps you understand what's expected. Remember that these scores are just one measure among many - your daily observations of your child's learning matter just as much.
