The Student Growth Percentile Model (SGP)
The Student Growth Percentile (SGP) model is a statistical approach used to measure individual student academic progress over time. Developed by Damian Betebenner in 2008, the SGP model has gained popularity in many states as a way to evaluate student growth and school effectiveness. Unlike traditional achievement measures that focus solely on proficiency levels, SGPs provide insight into how much progress a student has made relative to their academic peers.
Key features of the Student Growth Percentile model include:
Peer Comparison: SGPs compare a student‘s growth to that of their academic peers – students with similar score histories on state assessments.
Percentile Ranking: Growth is expressed as a percentile rank from 1 to 99, indicating the percentage of peers that a student outperformed in terms of growth.
Subject-Specific: SGPs are typically calculated separately for different subjects, such as math and reading.
Normative Measure: SGPs are normative, meaning they describe a student‘s growth relative to others rather than against a fixed standard.
Flexibility: The model can be applied to various types of assessments and across different grade levels.
To calculate SGPs, the model uses quantile regression to estimate the conditional distribution of current-year test scores, given prior test scores. This approach allows for the comparison of students with diverse starting points and accounts for the fact that students at different achievement levels may grow at different rates.
Advantages of the SGP model include its ability to provide a more comprehensive picture of student progress, its fairness in comparing students with different starting points, and its ease of interpretation for educators and parents. However, critics argue that the model’s relative nature makes it difficult to set absolute growth targets and that it may not fully account for external factors affecting student performance.
Many states use SGPs as part of their accountability systems, often combining them with achievement measures to evaluate school and teacher effectiveness. As education systems continue to emphasize growth alongside proficiency, the Student Growth Percentile model remains an important tool for understanding and promoting student progress.