A growth score measures how much a student has learned and progressed over time, comparing their improvement to peers with similar starting points rather than measuring achievement at a single moment.
What is a Growth Score?
A growth score tracks student learning progress over time rather than measuring achievement at a single point. The most common implementation is the Student Growth Percentile (SGP), which compares a student's growth to other students with similar prior test scores. SGPs range from 1 to 99, where a score of 85 means the student showed more growth than 85% of peers who started at a similar level. Unlike status scores that show where a student stands at one moment, growth scores reveal learning trajectory. This makes them particularly valuable for homeschoolers, where individual progress matters more than comparison to arbitrary grade-level standards.
Key Takeaways
- Growth scores measure progress over time, not achievement at a single point
- Student Growth Percentiles (SGPs) compare growth to academic peers with similar starting points
- A student can show high growth even with low absolute achievement, or vice versa
- NWEA MAP Growth uses the RIT scale for consistent year-over-year tracking
- Growth scores focus on 'Am I improving?' rather than 'Am I keeping up?'
How Growth Scores Differ from Other Metrics
Growth Score vs. Percentile Rank: Percentile rank compares current achievement to all same-grade peers. Growth score compares improvement to peers with similar prior scores. Two students with very different achievement levels can have identical growth scores. Growth Score vs. Grade Equivalent: Grade equivalent indicates the grade level at which a typical student would earn that raw score. Growth scores use consistent scales that track progress year over year without the interpretation problems of grade equivalents. The key insight: high achievement and high growth are not the same thing.
NWEA MAP Growth: The Most Common System
NWEA MAP Growth uses the RIT scale (Rasch UnIT), ranging approximately 100-350. This grade-independent scale allows tracking from kindergarten through 12th grade on the same continuum. The scale uses equal intervals, meaning the difference between scores is consistent regardless of achievement level. Computer-adaptive testing adjusts difficulty based on responses, finding the level where students answer correctly about half the time. Two types of norms exist: performance norms (comparing to grade-level peers) and growth norms (comparing to peers with similar starting points).
Value for Homeschoolers
Growth scores align with homeschooling's focus on individual progress. A student can score below grade level but still demonstrate excellent growth, validating your approach. Tracking growth over time helps identify when instruction is working versus when adjustments might be needed. Many states require evidence of "adequate educational growth and progress"; growth scores provide objective documentation beyond single-point achievement measures. Using the same assessment system year-over-year provides consistent data on learning trajectory. Growth scores reduce the pressure of "keeping up with others" by focusing on "Am I progressing?"
The Bottom Line
Growth scores reveal what homeschool parents most want to know: is my child learning and progressing? Unlike achievement scores that compare to grade-level expectations, growth scores track individual improvement over time. A single growth score has limited meaning, but tracking growth across multiple testing periods reveals learning patterns that inform instructional decisions. Consider using consistent assessment tools like NWEA MAP year-over-year to build meaningful growth data. Focus on progress, not just position.
